WASHINGTON (Reuters) - Several U.S. states and immigrant advocacy groups vowed on Tuesday to fight President Donald Trump’s decision to end a program that protects people brought illegally to the United States as children from deportation. But legal experts said the challenges will face an uphill battle. Democratic state attorneys general in California, New York, Washington and Massachusetts said they will sue to defend the Obama-era policy known as Deferred Action for Childhood Arrivals, or DACA, and the immigrants known as Dreamers. “We are going to court to defend DACA and to fight for these Dreamers,” said Massachusetts Attorney General Maura Healy. The states have not said what their legal claims will be.     The Trump administration on Tuesday announced it would phase out the program but urged Congress to enact immigration reform if it wants to protect DACA recipients. [nL2N1LM0HT] Whatever lawsuit the Democratic states file, winning will not be easy, said Jonathan Adler, a law professor at Case Western Reserve University College of Law. “DACA did not create any legally enforceable rights, and certainly did not create any right to indefinite presence in the country,” he said. One immigrant group, the National Immigration Law Center, has already filed court papers seeking to block the Trump administration’s action by amending an existing lawsuit pending in New York. The case was filed last year on behalf of DACA recipient Martin Batalla Vidal, an immigrant from Mexico who came to the United States when he was 7. It originally contested a ruling enjoining a program of former President Barack Obama that offered protection to undocumented parents of U.S. citizen children.  In the new filing, Vidal’s lawyers outlined a two-prong challenge to Trump’s DACA action. One claim was that the move violated the federal Administrative Procedure Act, a law requiring government agencies to follow set processes when making major policy changes. Batalla Vidal’s lawyers said Trump’s announcement was an “abrupt policy shift” affecting nearly 800,000 program participants who had assumed the protections would remain in place.  Trump promised during his presidential campaign to dismantle DACA but since taking office in January has taken a softer tone. The lawyers noted that he told DACA recipients he would “take care” of them. The filing also asserts that the new policy is discriminatory and was “substantially motivated by the animus of the president and his administration toward Latinos and Mexicans.”  Stephen Yale-Loehr, an immigration law professor at Cornell Law School, said any litigation against Trump’s action will face multiple obstacles. Among them is the fact that courts are “generally more deferential to immigration actions by the executive branch than in other areas, because immigration touches on sovereignty and national security,” he added. 
U.S. states, immigrant groups to fight Trump's Dreamer decision