Protests erupt after Poland approves its SOPA WARSAW, Poland - Poland on Thursday signed an international copyright agreement, sparking more demonstrations by Internet users who have protested for days over fear it will lead to online censorship. After the signing, protesters rallied in the Polish cities of Poznan and Lublin to express their anger over the treaty. Lawmakers for the left-wing Palikot's Movement wore masks in parliament to show their dissatisfaction, while the largest opposition party, the right-wing Law and Justice party, called for a referendum on the matter. Controversy in Poland has been deepening over the Anti-Counterfeiting Trade Agreement, or ACTA. Though many other industrialized countries have signed it, popular outrage appears to be greater in Poland than anywhere else. Hysterical over SOPA for all the wrong reasons SOPA is dead, Smith pulls bill PIPA, SOPA put on hold in wake of protests ACTA is a far-reaching agreement that aims to harmonize international standards on protecting the rights of those who produce music, movies, pharmaceuticals, fashion, and a range of other products that often fall victim to intellectual property theft. ACTA also takes aim at the online piracy of movies and music; those opposed to it fear that it will also lead authorities to block content on the Internet. A prominent Polish rock start, Zbigniew Holdys, has come out in support of ACTA, accusing the Internet activists, mostly young people, of profiting from pirated material online and trying to hold onto that practice. ACTA shares some similarities with the hotly debated Stop Online Piracy Act in the U.S., which was shelved by lawmakers last week after Wikipedia and Google blacked out or partially obscured their websites for a day in protest. Poland's ambassador to Japan, Jadwiga Rodowicz-Czechowska, signed it in Tokyo. Speaking on Polish television, she said that Poland was one of several European Union countries to sign ACTA Thursday, including Finland, France, Ireland, Italy, Portugal, Romania and Greece. Several other industrialized countries, including the United States, Canada and South Korea, signed the agreement last year. Poland's support for ACTA has sparked attacks on Polish government websites by a group calling itself "Anonymous" that left them several of them unreachable off and on for days. Street protests of hundreds, and in some cases thousands of people, have broken out across Poland for the past three days. In reaction to the widespread opposition, Polish leaders have been struggling to allay fears over it. Poland's Foreign Minister Radek Sikorski defended his government's position in a TV interview Wednesday evening, arguing that ACTA is not as threatening as young people fear. But he said the Internet should not be allowed to become a space of "legal anarchy." "We believe that theft on a massive scale of intellectual property is not a good thing," Sikorski said. In the Czech Republic, a local group aligning itself with Anonymous attacked the website of a group that supports ACTA. The group collects money for music production and distributes it to artists.