European lawmakers are about to vote on a piece of legislation that critics say would significantly damage internet freedom.

Parliamentarians in Strasbourg, France, will cast their votes on the European Union’s new copyright directive on Thursday. The regulation is an update to a 2001 directive on copyright, and is aimed at modernizing those rules for the digital age.

Under the new directive on copyright, online content platforms like Google and Facebook would be required to use filtering systems that block content — such as images and videos — that infringes the rights-holder’s copyright.

In addition, “new media” publishers would essentially be required to pay news organizations for the rights to share articles and other copyright-protected content, something critics claim is an effective “tax” on links.

This could have a particularly damaging effect on the likes of Google, Facebook and Twitter, whose platforms rely on the sharing of news content, images and videos.

The copyright regulation is part of the EU’s “digital single market,” a strategy aimed at setting a common standard for online services and businesses.

In protest of the law, the Italian and Spanish-language versions of Wikipedia blocked access to users earlier this week, arguing the law will impose “new barriers, filters and restrictions” that prevent users from being able to share content.

Wikimedia — which hosts the popular online encyclopedia — is one of a number of opponents of the law, slamming it as a “threat to our fundamental right to freely share information.”

Mozilla, the firm behind the internet browser Firefox, is also opposed, and argues the law could “make filtering and blocking online content far more routine.”

And Tim Berners-Lee, the inventor of the World Wide Web, and Jimmy Wales, the founder of Wikipedia, were among a number of high-profile industry figures to co-sign an open letter last month lambasting the proposed law as an “imminent threat” to the future of the internet.

Activists are concerned that the law could stop people from posting everything from an internet meme to a news article.

Particular controversy has surrounded two key parts of the law — Article 11 and Article 13. The former grants news outlets copyright over the sharing of their content online, while the latter calls for “effective content recognition” systems to be put in place by tech companies to prevent copyrighted materials from being posted on digital platforms.

Memes, a central part of internet culture, often rely on the use of copyrighted images, usually for a comedic effect.

The law would place the onus on platforms like Facebook, Twitter and YouTube to take down copyrighted content, rather than the owners of intellectual property to make a claim against that content being used without authorization.

The directive has already been passed by a European parliamentary committee, and will now be under the lens of the whole European Parliament.

The legislation has not arrived out the blue — it was first proposed by the European Commission, the EU’s executive body, in 2016.

“I think it is a bit of a surprise to the public, but that’s because it’s become a bit more real now that the committee votes have taken place and it’s going forward to the European Parliament,” Jim Killock, executive director of Open Rights Group, an anti-censorship organization, told CNBC.

Killock added: “There is now on the internet a big culture of people reusing copyright works and the thing that’s caught everyone’s attention are memes, which is clearly a use of copyright work. The question is whether that’s infringing

It’s important to remember that internet giants like Google are opposed to the law as it would impact their business model. According to music industry body U.K. Music, Google has spent 31 million euros ($36 million) on lobbying efforts, directly and indirectly.

But the controversial directive is not without its backers.

Multiple figures in the music industry — including artists as big as Paul McCartney — are proponents of the law, and argue that it is intended to secure revenues for artists that would otherwise be lost from the unauthorized use of their material on content-sharing platforms like YouTube.

In an open letter to members of the European Parliament ((MEPs) on Wednesday, McCartney pleaded with lawmakers to support the copyright overhaul.

“We need an internet that is fair and sustainable for all,” the former Beatles star said. “But today some user upload content platforms refuse to compensate artists and all music creators fairly for their work, while they exploit for their own profit.”

Axel Voss, a German MEP for the conservative European People’s Party, said that criticisms of the copyright directive were misleading. He said that the law would not lead to the censorship of memes.

“I can’t see why our proposal should lead to something like this,” Voss told CNBC. “If we are looking to memes, the legitimate use of memes is not a question of Article 13, it is of copyright. This is nothing new.”

He added: “If you have an exception under the general copyright law for creating memes and this is legitimate, then of course you can still upload these, there is nothing that should hinder this.”

Voss said that the law would not result in automated filtering systems that routinely block content that is thought to breach copyright.

“From my understanding, this is not leading to censor machines and upload blockers,” he said.

Once the vote has taken place, lawmakers and member states will debate it further behind closed doors, a process that could speed up its passage into law. If members of the European Parliament reject it, there will be a chance to amend the law.