BERLIN – Braving subzero temperatures, hundreds of thousands of Europeans across the continent took to the streets Saturday, protesting an international trade agreement many say will overrule democratic institutions, jeopardize civil liberties and stifle technological innovation.

The Anti-Counterfeiting Trade Agreement (ACTA) is designed to put in place international standards to protect intellectual property rights. But some lawyers say it forces private companies to police cybertraffic — and across the globe the treaty is being seen as a serious threat to Internet freedom.

"It's becoming an issue of citizens' power," said David Hammerstein, senior adviser on intellectual property for Trans-Atlantic Consumer Dialogue, an umbrella consumer rights organization in Brussels. "The front lines of the defense of civil rights today is the defense of an open, free Internet and that (is what ACTA threatens.)"

Critics say that the details of ACTA have been decided behind closed doors, a deliberate move to slip the highly controversial agreement through without proper public scrutiny. They add that once they have signed up countries have no say in any subsequent changes to the treaty.

When the European Union signed ACTA on Jan. 26, the European Parliament's rapporteur on ACTA, Kader Arif, resigned, calling the entire process a "charade" designed to prevent the European Parliament having any say in an agreement that could have a "major impact on citizens' lives."

The European Parliament still needs to sign off on the treaty by June.

The agreement has been signed by 22 of the 27 EU member states, but countries including Germany and the Czech Republic have yet to do so, and some others are now backing off.

Slovenia's ambassador to Japan, Helena Drnovsek Zorko, has publicly apologized for signing the treaty, saying that it "limits and withholds the freedom of engagement on the largest and most significant network in human history, and thus limits particularly the future of our children."

Zorko also encouraged Slovenians to join demonstrations organized via Facebook against ACTA in Ljubljana last weekend. Thousands have already taken to the streets of the Slovene capital.

In Budapest, the anti-ACTA march was also the first demonstration of the "Occupy Budapest" movement. Crowds gathered in front of lawmakers' offices to listen to speakers, some of whom who wore masks to conceal their identity.

Protests shivered but said they were glad to be there.

"I am here to protest against others' rights to collect information about me that I never intended to share with them," said Aniko Kapeller, a graphic designer who lives in Budapest.

"ACTA does not only violate the rights of file-sharers while serving a small interest group, but also more severely limits the freedom of the Internet even more acutely," said Sandor Szorad, a student protesting in Budapest. "It provides for the unlimited surveillance of people's activities on the net, without giving them the benefit of the doubt. All freedom-loving people have to protest against this."

In Vilnius, Lithuania, the arctic weather kept many people at home. About 500 came to protest the ACTA treaty at a square near federal buildings even though 10 times that number registered to participate via Facebook. Protesters held signs reading "Corporations + governments = ACTA."

And across Germany, thousands marched against the treaty in Munich, Oldenburg and Berlin.

In Berlin, where a youthful crowd made for a carnival atmosphere, about 6,500 protesters were out on the street, according to police estimates. Organizers, who had been expecting 500, said the turnout was overwhelming. .

"It's so great to see so many young people brave the cold [to come out and protest] this issue," said Anne Meyer of Berlin.

Confronted with what some are calling the biggest public demonstrations in Poland's post-communist history, Prime Minister Donald Tusk has called a halt on ratifying the agreement.

"We all kind of went crazy over this issue," said Tusk during a debate over ACTA last weekend. "No other country saw such large-scale protests. We had almost hell here, which means that there is a problem with the (treaty)."

For Romanian exporters, "ACTA will help protect international markets, the intellectual and industrial property rights, copyrights, trademarks, patents and designs," said Ioana Muntean, a spokeswoman for the Romania government.

"Slovakia has already adopted a lot of legislation that matches ACTA: It means we already do what this treaty requires," said attorney Adriana Tomanova, director of the Slovak Association for Protecting Authors´ Rights.

In a joint statement on the governing Christian Democrats/Christian Social Union's website, deputy parliamentary party leader in the Bundestag Günter Krings and the rapporteur on copyright law for the German legal affairs committee Ansgar Heveling reiterated the party's commitment to "strong protection for intellectual property even in the digital age." But they stopped short of endorsing ACTA.

The most widespread criticism focuses on the fear that it will lead to Internet censorship by allowing Internet service providers to be held accountable for its customers' online content, something which Hammerstein likens to "asking the post office to be responsible for what is inside packages."

"In order to comply with ACTA, Internet providers would have to start monitoring the Internet and look at what individual users do in terms of file sharing and so on," said Joerg Hladjk a lawyer specializing in data privacy at Hunton & Williams' Brussels office. This he says, comes into direct conflict with fundamental rights under European data protection law.

Critics are also concerned that the treaty is ambiguous on what constitutes a breach of intellectual copyright protections, leaving courts in individual countries to decide.

"ACTA threatens honest Internet users who don't try to steal intellectual property," said Armands Leimanis of Latvia's anti-ACTA movement. "It is specifically dangerous for Latvians. Latvian copyright holders' organizations are incompetent, and if they are given more authority it will be dangerous."

Latvia withdrew ACTA from the ratification process in parliament this week in the face of mounting protests. And Slovakia has delayed putting the treaty into the ratification process.

Supporters of ACTA say the agreement is there to protect the rights of creative industries to earn money from their innovations and that ACTA is flexible enough to allow for a balance between competing interests. But some say that beyond copyright concerns, ACTA is an attempt to seize control of what has become an ungovernable realm where citizens are seen to have too much power.

"I think there is also a political agenda behind controlling Internet, aside from business (interests), where governments feel that the Internet is out of hand, it's out of control and (they) want to regain control," Hammerstein said. "There is a very fine line between political repression and IPR repression and we have seen it many countries, in Iran, in Russia, in China, where under the excuse of copyright there have been politically repressive measures."

Also, the treaty makes what have previously been civil and commercial disputes over intellectual property rights criminal matters. Critics say the threat of jail sentences and "sky's the limit" financial penalties could prevent the kind of innovation that has given the world Google, Skype, Facebook and Twitter.

The agreement was signed by the United States, Australia, Canada, Japan, Morocco, New Zealand, Singapore and South Korea in October last year. But with 2 million people signing an online petition against ACTA , activists hope the widespread anger among citizens will put a stop to Europe adopting the treaty.

"I think if people are on the streets protesting against it, the European Commission will rethink it," said Stephan Urbach of Germany's Pirate Party, which was involved in organizing the protests across Germany. "This is something that is bringing people all over Europe out on the streets, together on the same day, for the same reason. We have not had anything like that for years."