Stephen Vickers, who oversaw police criminal intelligence in Hong Kong before Britain returned the territory to China in 1997, said Saturday that the police could detain Mr. Snowden if Hong Kong government lawyers determine that the charges he faces in the United States are also illegal offenses in Hong Kong, which is likely. 
 
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 “I have no doubt whenever the government decides to take action, they will pick him up fast,” said Mr. Vickers, who now runs a risk consulting firm. 
 
 David H. Laufman, a former federal prosecutor, said that American officials are likely to press Hong Kong to make sure Mr. Snowden no longer has access to the news media while in custody for fear that he could reveal more N.S.A. secrets. “He’s a walking disclosure time bomb,” Mr. Laufman said. 
 
 If and when the Hong Kong police detain him, Mr. Snowden can then appeal to a magistrate for his release. But he faces another complication: his 90-day tourist visa runs out in mid-August, giving the local authorities another reason to keep him in custody. Should he go to jail, Mr. Snowden would “have slightly greater privileges than prisoners” elsewhere in Hong Kong, said a lawyer with experience in Hong Kong extradition cases, including the choice of Chinese or Western food and access to books — but not to computers. 
 
 The more daunting challenge facing the United States is its request to have Mr. Snowden sent back to face charges in the Eastern District of Virginia. Federal prosecutors there have handled many major national security cases, and Mr. Snowden’s most recent employer, the N.S.A. contractor Booz Allen Hamilton, has headquarters in the district. 
 
 A senior Obama administration official suggested on Saturday that strong pressure was being applied privately on the Hong Kong authorities to swiftly return Mr. Snowden. “If Hong Kong doesn’t act soon, it will complicate our bilateral relations and raise questions about Hong Kong’s commitment to the rule of law,” the official said. 
 
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 But the appeal to the rule of law cuts both ways, because the United States’s surrender treaty with Hong Kong has an exception for political offenses. Mr. Snowden and his lawyers, whom associates say he has retained but who have not been publicly identified, could tie up the extradition effort by asserting that his alleged crimes are political in nature, said Regina Ip, a former Hong Kong secretary of security and a current legislator. She added that such an assertion would have “to go through various levels of our courts.” 
 
 Alternatively, Mr. Snowden could apply for asylum. Currently, asylum claims are facing delays of several years in Hong Kong, because they are handled by Hong Kong officials in cooperation with the office of the United Nations High Commissioner for Refugees. Nazneen Farooqi, a local protection officer with the United Nations refugee agency, suggested last week, without addressing Mr. Snowden’s case directly, that his case would not be fast-tracked should he go this route, since “we prioritize older cases.” And people who make asylum applications can be held in detention for weeks, months or even longer. 
 
 Then there is the question of popular pressure in China to protect Mr. Snowden from punishment. In recent weeks, Mr. Snowden’s plight has been seized on by several groups: by Hong Kong’s human rights movement, by pro-Beijing activists attracted to his defiance of the United States, and by those angered by Mr. Snowden’s claims that Hong Kong was itself the target of aggressive American surveillance efforts. 
 
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 A Hong Kong newspaper, The South China Morning Post, reported late on Saturday additional details of the N.S.A.’s spying on Hong Kong and China, apparently based on an interview with Mr. Snowden on June 12. Mr. Snowden told the newspaper that the N.S.A. had tapped into Chinese mobile phone companies to read millions of text messages, hacked dozens of computers at Beijing’s prestigious Tsinghua University and other computers operated by Pacnet, a major telecommunications company with headquarters in Hong Kong and Singapore. 
 
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 While there was no independent confirmation of the claims, all the operations described by Mr. Snowden are consistent with the N.S.A.’s aggressive monitoring of foreign communications. And the newspaper’s report could win Mr. Snowden more public support in China and Hong Kong. 
 
 Finally, China could apply behind-the-scenes pressure to slow down or block the effort to have Mr. Snowden turned over. Hong Kong enjoys legal autonomy from mainland China, but the Chinese government can intervene in diplomatic and defense matters. 
 
 While Chinese officials have steered away from commenting on the specifics of Mr. Snowden’s case, government and news outlets controlled by the Communist Party have been increasingly sympathetic to Mr. Snowden, with an opinion article in the state-run China Daily suggesting Thursday that “Snowden’s crime, if any, pales in comparison with the actions of the U.S. officials who authorized and operated the cyberespionage program.” 
 
 Overwhelming majorities in both parties in Congress appear to support the prosecution of Mr. Snowden. But his revelations have already produced some uncomfortable moments for the administration: a Republican congressman who helped write the Patriot Act, Representative Jim Sensenbrenner of Wisconsin, declared one leaked N.S.A. program “un-American,” and the director of national intelligence, James R. Clapper Jr., was forced to admit that his previous statement to Congress that the agency did not collect records on millions of Americans was untrue. 
 
 Mr. Snowden is the seventh person to be accused by the Obama administration of violating the Espionage Act of 1917 by leaking secrets to the news media, compared with three such cases under all previous presidents. And unlike others accused of leaking, Mr. Snowden went public with his own explanation of his actions before he was charged, telling The Guardian that his leaks were an act of conscience intended to give Americans a chance to decide the appropriate limits of spying. He has drawn support from a wide swath of the political left and the libertarian right in the United States. 
 
 Even if he is silenced by the Hong Kong authorities during a removal battle, his supporters will echo and amplify his claim to have acted in the interest of democracy. Mr. Obama, who said after the leaks surfaced that he welcomed a debate over surveillance programs, will preside symbolically over the pursuit and punishment of the man who started the debate. 
 
 “For better or worse, it’s the president’s prerogative to decide what’s classified and what’s not,” said Stephen I. Vladeck, a law professor at American University. “But it’s reasonable to think that the administration deserves some blame for leaving it to people like Snowden to start a public debate on these issues.” ||||| Edward Snowden's choice of Hong Kong as a haven from where to leak intelligence documents and to unmask himself as a whistleblower rests on calculations on the territory's press freedom safeguards and its extradition treaty with the US. It is a high-stakes gamble. 
 
 Just before sovereignty over Hong Kong passed from Britain to China in 1997, the US signed a new extradition treaty with the semi-autonomous territory. Under that treaty, both parties agree to hand over fugitives from each other's criminal justice systems, but either side has the right of refusal in the case of political offences. 
 
 Beijing, which gave its consent for Hong Kong to sign the agreement, also has a right of veto if it believes the surrender of a fugitive would harm the "defence, foreign affairs or essential public interest or policy'' of the People's Republic of China. In short, the treaty makes Snowden's fate a matter of political expediency not just in Hong Kong but in Beijing. 
 
 In his Guardian interview, Snowden denied that his decision to fly to Hong Kong to make his allegations on NSA intrusion and infringement of American civil liberties was intended as a vote of confidence in Chinese human rights. But he noted that the people of Hong Kong have "a spirited commitment to free speech and the right of political dissent". 
 
 Certainly in comparison with mainland China, Hong Kong is an island of press freedom and political tolerance. When the UK ended 156 years of colonial rule and Hong Kong became China's first 'special administrative region', it was given special status under the principle of "one country, two systems". Most importantly, Hong Kong has its own constitution, its Basic Law, giving it a "high degree of autonomy" on all issues except foreign relations and defence. 
 
 The territory has multi-party politics but its chief executive is chosen by an election committee of just a few hundred electors. The freedom of the Hong Kong press, meanwhile, is being continually put to the test. When the government attempted in 2003 to impose restrictions on the grounds of sedition and national security, half a million people came out to demonstrate and the bill was withdrawn. 
 
 The tradition of commemorating the 1989 killing of Tiananmen Square demonstrators – banned in the rest of China – is vigorously upheld in Hong Kong. Attendance at a memorial ceremony in the territory's Victoria Park last week was estimated at between 54,000 and 150,000, despite torrential rain. 
 
 The combination of a comparatively liberal civic culture and the sovereignty of Beijing, America's great Pacific rival with which it has an often testy relationship, seems to have been a factor in Snowden's choice of Hong Kong. It may play to his advantage that Presidents Barack Obama and Xi Jinping reportedly agreed to differ on cybersecurity issues in their weekend summit in California. Against this background, Snowden's extradition might be seen in the party leadership in Beijing as a capitulation. But such calculations can change. 
 
 "Call me naive but I think this is going to come down to how Beijing wants to play this," Josh Marshall argued on his Talking Points Memo blog. "If they don't want a fight over this, Snowden's toast. If they like the optics of it, I don't think it matters what that extradition treaty says. China's a big enough player and the US has enough other fish to fry with the Chinese, that the US is not going to put the bilateral relationship on the line over this guy." 
 
 • This article was amended on 28 June 2013 to amend a reference to Hong Kong passing its own Basic Law. ||||| Hundreds of demonstrators have taken to the streets of Hong Kong despite heavy rain to support the NSA whistleblower Edward Snowden and press the US to change its surveillance policies. 
 
 The gathering on Saturday came hours before Hong Kong's chief executive, CY Leung, broke days of silence on the case. He promised to "follow up on any incidents related to the privacy or other rights of the institutions or people in Hong Kong being violated". 
 
 His spokesman declined to elaborate on what that follow-up may entail, the South China Morning Post said. 
 
 Snowden has alleged that the US hacked hundreds of targets in Hong Kong and on mainland China. 
 
 Leung's statement said the government would handle Snowden's case "in accordance with the laws and established procedures of Hong Kong". 
 
 Human rights groups and other organisations arranged the rally after Snowden, a US citizen, told the South China Morning Post that he planned to stay in the territory and "ask the courts and people of Hong Kong to decide my fate". Three days earlier he revealed his identity and his presence in Hong Kong in a video interview with the Guardian. 
 
 Protesters waved placards and chanted "protect free speech – protect Snowden" as they rallied in the centre of the city before marching past the US consulate and gathering outside government offices. 
 
 Hong Kong has a well-used surrender treaty with the US. Supporters say they are concerned that Beijing may intervene in the decision and are worried about his treatment if he is sent back to the US. 
 
 Legislator Charles Mok told the crowd of more than 500 that they were there to protect not just Snowden but "all of us", given the allegations about US surveillance. 
 
 Albert Ho Chun-yan, a high-profile Democratic politician, said: "It's unlawful, unjustified and unscrupulous … We demand the whole truth be disclosed by the US administration, an unconditional apology from [President Barack] Obama and an assurance this interference will stop." 
 
 Allen Kuo, 43, who works in finance, said that as an American the behaviour of the US was "an embarrassment". Holding a sign reading "We stand with Snowden", he said: "People say he is a traitor and what he has done is illegal. I think spying on American people is unconstitutional and we need to address that first." 
 
 Protestors came from a range of ages and nationalities. Teacher Mary Stickley, who has lived in Hong Kong for 17 years, said: "This is my first ever march; I just felt pretty strongly about it." 
 
 Ruth Jopling, whose two young daughters were clutching Snowden masks, said: "We think it does not just affect us, but the next generation. That's why we have come as a family. It's time to stand up: he came to Hong Kong, so he must trust us to do something, and it's not good if we let him down." 
 
 One placard in the crowd read "Read my lips, not my emails". Others had images of Obama above the slogan "Big brother is watching you". 
 
 Several pictured both the US president and the Chinese leader, Xi Jinping, reinforcing the message from many protesters that they should not have to choose between criticising the US or Beijing. 
 
 Oiwan Lam, one of the rally's organisers, said: "In the past we have campaigned against Beijing, usually against their violations of rights and free speech … It's not fair to use one evil to cover another." 
 
 Tsui Hon Kong, of the Professional Teachers Union, which backed the protest, compared Snowden's case to that of a Chinese journalist who leaked a propaganda directive banning discussion of the anniversary of the 1989 crackdown on the student protests in Tiananmen Square. Shi Tao was jailed after Yahoo handed email records to the Chinese government. 
 
 Tsui said the case was similar because it was about governments ordering internet providers to give them information about customers. "The important thing is that many Americans came forward to speak up for Shi Tao. Now it's our turn," he said. 
 
 Several hundred people participated, but the numbers were small compared with other recent demonstrations. A vigil on the anniversary of the 1989 crackdown this month drew tens of thousands. 
 
 A small poll conducted for the South China Morning Post found that one in two Hong Kong residents did not believe Snowden should be returned if the US made a surrender request. 
 
 Half of the 509 respondents in the poll, conducted by the Centre for Communication and Public Opinion Survey at Chinese University, said they were against or strongly against his surrender, the Post reported. 
 
 Nearly one in five said Hong Kong should hand him over, and the remainder refused to answer or said they had not formed an opinion.
– While Hong Kong is undoubtedly a more pleasant place to spend time than an Ecuadorian embassy—let alone a US prison—analysts are baffled by NSA whistleblower Edward Snowden's decision to take refuge there, as are lawmakers in the largely self-governing Chinese territory. Hong Kong has an extradition treaty with the US, though Beijing maintains the right of veto over it, notes the Guardian, calling Snowden's move a "high-stakes gamble" that makes his fate "a matter of political expediency." What's more, CNN adds that hotel costs will soon max out Snowden's limited funds. (And then there's the stir-crazy factor; he has apparently left his room just three times in the last three weeks.) Snowden—who admits he doesn't expect to see home again—says he chose Hong Kong because they "have a spirited commitment to free speech and the right of political dissent," though his first choice for asylum would be Iceland, CNN reports. Some Hong Kong politicians say the territory's history of working closely with the US makes it a poor choice for Snowden—though others say they are "flattered." A criminal investigation into the leak has begun and the US is expected to begin extradition proceedings soon; a long legal battle in Hong Kong could ensue before Beijing decides on using its veto, the Wall Street Journal reports. In the meantime, Snowden has gotten his very own White House petition, with some 8,734 people, at the time of this writing, requesting "a full, free, and absolute pardon" for the "national hero."