Notorious and controversial imageboards 4chan and Kiwi Farms are taking the UK government to task in U.S. federal court, filing suit against the country’s Office of Communications (Ofcom) over the controversial Online Safety Act (OSA).

The lawsuit, filed on Wednesday, August 27, follows earlier threats made by the site’s legal counsel, Preston Byrne. Byrne warned that the platforms would challenge Ofcom’s attempts to levy fines and penalties under the OSA. Their goal is clear: to have U.S. courts recognize the UK’s sweeping internet law as unenforceable on American companies that operate entirely outside the UK.

Since taking effect on July 25, the OSA has introduced broad age verification requirements that force UK citizens to provide proof of age to access even mainstream platforms like YouTube and Spotify. The law, billed as protecting children from "harmful" content like pornography, has instead drawn fire from critics who argue it undermines privacy, restricts access, and effectively walls off parts of the internet.

Noncompliant sites like 4chan and Kiwi Farms have faced threats of fines and outright blocking in the UK. Both platforms argue that Ofcom has no jurisdiction over them since their servers and operations are based in the United States. The lawsuit marks the most significant legal challenge yet to the OSA, which has already proven to be one of the most controversial internet laws in recent memory.

In a statement to Mashable, a spokesperson with Ofcom stated the following:

“We are aware of this lawsuit. Under the Online Safety Act, any service that has links with the UK now has duties to protect UK users, no matter where in the world it is based. The Act does not, however, require them to protect users based anywhere else in the world.”

According to the lawsuit, 4chan alleges that Ofcom has threatened to slap the site with an £18 million ($24 million) fine and warned that site operators could even face prison time if they refused to comply with the Online Safety Act.