TikTok, in addition to its Chinese parent company ByteDance, is suing to block the so-called “TikTok ban” President Biden signed into law two weeks ago. Both companies filed the lawsuit with the U.S. Court of Appeals for the District of Columbia Circuit on Tuesday, claiming the law is unconstitutional and violates the First Amendment.

It’s not a surprise move by any means: TikTok CEO Shou Zi Chew previously said the company would fight the law in court. Chew and and the company believe U.S. law is on their side, and that Congress’ law won’t stand up in court. Congress, however, worked with the Department of Justice on the law in the first place, so lawmakers are confident it will stand up to scrutiny.

The “TikTok ban” gives parent company ByteDance nine months to sell the app to a company not based in China. If ByteDance shows it is trying to sell, or is in the middle of a sale, President Biden can extend the timeline by 90 days. That means, at most, ByteDance has until April 2025 to find someone to take the app of their hands.

For TikTok’s U.S. operations, however, this fight is existential, as ByteDance says it won’t sell the app. If the company sticks to its word, TikTok will be removed from app stores in the U.S. by January, unless it can win in court.

Why does the U.S. government want to ban TikTok?

Lawmakers in Congress have been worried about TikTok for years. There are two key concerns: The app is owned by a Chinese company, which is bound by law to disclose user data to the Chinese government if requested. Lawmakers see that as a potential security risk for American users, as the Chinese government could possibly gather their personal data.

The other side of the coin concerns the content Americans see on the app: Lawmakers worry the Chinese government could manipulate the videos that TikTok delivers to U.S. users in a way that benefits China. The government already has a heavy hand in the content shown on Douyin, the Chinese version of TikTok. TikTok says it does not give U.S. user data to the Chinese government, and denies the claim the government has a hand in the content Americans see.

While the concerns are mostly hypothetical, there have been instances that have proven Congress’ concerns valid: ByteDance employees were able to obtain the IP addresses of American journalists from their TikTok accounts, and in July, we learned some American user data was indeed stored in China, contradicting TikTok’s claims.

While Congress doesn’t have the best reputation for their tech savviness, TikTok has done little to assuage their concerns. In fact, when they called upon their user base to flood Congress with messages of disdain for the TikTok ban, lawmakers only saw more reason than ever to pass the bill.

For a complete timeline of the U.S. government’s fight against TikTok, check out our explainer here.