The Supreme Court’s remarkably speedy decision Friday to allow a controversial ban on TikTok to take hold will have a dramatic impact on the tens of millions of Americans who visit the app every day and broad political implications for President-elect Donald Trump.

The app had more than 170 million monthly users in the U.S. The black-out is the result of a law forcing the service offline unless it sheds its ties to ByteDance, its China-based parent company.