US state votes to ban TikTok for first time - but how would Montana's law work?
The state had already banned the app on government devices but this extends the prohibition to personal phones.
Montana has passed a bill banning TikTok in the state.
The state House voted 54-43 to pass the bill - which goes further than prohibitions in place in nearly half the states and the US federal government that prohibit the video-sharing app on government devices.
The measure now goes to Republican Governor Greg Gianforte for his consideration.
The bill, known as SB-419, cites a number of concerns about the app, including alleged surveillance from the Chinese government and encouragement of "dangerous activities" among young users, such as "throwing objects at moving automobiles" or "lighting a mirror on fire and then attempting to extinguish it using only one's body parts".
The legislation makes it illegal for app stores to offer TikTok, however it does not prevent those who already have the app from using it.
Violations of the bill could carry a penalty of up to $10,000 (£8,000), which would be enforced by Montana's Department of Justice.
Montana already bans the app on state-owned devices.
TikTok spokesperson Brooke Oberwetter said in a statement: "We will continue to fight for TikTok users and creators in Montana whose livelihoods and First Amendment rights are threatened by this egregious government overreach."
The bill's supporters "have admitted that they have no feasible plan for operationalising this attempt to censor American voices and that the bill's constitutionality will be decided by the courts", Ms Oberwetter said.
TikTok, which is owned by the Chinese tech company ByteDance, has been under intense scrutiny over concerns it could hand over user data to the Chinese government or push pro-Beijing propaganda and misinformation on the platform.
Leaders at the FBI, CIA and numerous lawmakers of both parties have raised those concerns but have not presented any evidence that it has happened.
Supporters of a ban point to two Chinese laws that compel companies in the country to cooperate with the government on state intelligence work.
TikTok has said its servers containing information on US users are in Texas.