Donald Trump, the president said that he wants to ban TikTok. Would such a ban violate the first amendment? If not does he have the power to act via executive order or does it have to go through Congress?
He has that power, as spelled out here, relying primarily on 50 U.S.C. 1701. This executive order already exists, so one path is to simply put Tik Tok on the Commerce Department's entity list. The specific list as of July 22 is here – you can find Huawei already on the list, for example. A First Amendment lawsuit is not likely to succeed, since there is no First Amendment right to directly or indirectly threaten national security, foreign policy, and the US economy (the compelling government interest). The courts will generally defer to the executive branch in its judgment regarding the necessity of a restriction. You could argue (as a proponent of Bytedance's side) that it is only necessary to ban the program on military devices, but the counter-argument is that a less restrictive action is not effective in addressing the compelling governmental interest.