The U.S. government and TikTok will go head-to-head in federal court on Monday as oral arguments begin in a consequential legal case that will determine if – or how — a popular social media platform used by nearly half of all Americans will continue to operate in the country.

Attorneys for the two sides will appear before a panel of judges at the federal appeals court in Washington. TikTok and its China-based parent company, ByteDance, are challenging a U.S. law that requires them to break ties or face a ban in the U.S. by mid-January. The legal battle is expected to reach the U.S. Supreme Court.

The law, signed by President Joe Biden in April, was a culmination of a years-long saga in Washington over the short-form video-sharing app, which the government sees as a national security threat due to its connections to China. But TikTok argues the law runs afoul of the First Amendment while other opponents claim it mirrors crackdowns sometimes seen in authoritarian countries abroad.