A US judge has blocked Montana’s first-of-its kind state ban on the use of short-video sharing app TikTok from taking effect on 1 January, saying it violated the free speech rights of users.

In a preliminary injunction on Thursday, US district judge Donald Molloy said the law “oversteps state power and infringes on the constitutional rights of users”.

The decision marks a major victory for a company that has been targeted by criticism and proposed regulation during its meteoric rise, including threats of a federal ban that gained momentum earlier this year. TikTok, which is owned by the Chinese parent company ByteDance, did not immediately comment.

Montana became the first state to ban TikTok in May when it passed legislation that would target marketplaces like the Google Play Store and the App Store, forbidding them from making the app available to users and fining them up to $10,000 per violation. Under the law, individual users would not be penalized.

TikTok sued Montana in May shortly after Governor Greg Gianforte signed the bill into law, arguing the legislation violated the first amendment free speech rights of the company and users. TikTok users in Montana also filed suit to block the ban.

The state attorney general’s office, which defended the ban approved by the legislature citing concerns about the personal data of Montana users and potential Chinese spying, did not immediately comment.

TikTok said in previous a court filing it “has not shared, and would not share, US user data with the Chinese government, and has taken substantial measures to protect the privacy and security of TikTok users”.

Molloy, who was appointed to the bench by Bill Clinton, found merit to numerous arguments raised by TikTok in his 48-page opinion – including that the law would cause irreparable harm to the company, and that TikTok has a number of safeguards in place surrounding user data.

“While there may be a public interest in protecting Montana consumers, the state has not shown how this TikTok bill does that,” he said.

During an October hearing, Molloy questioned why no other state had followed Montana in banning TikTok and asked if the state was being “paternalistic” in arguing the ban was necessary to protect the data of TikTok users.

The opinion stated that an estimated 150 million people in the United States access TikTok every month, including over 380,000 people in Montana. The judge’s injunction will halt Montana’s ban pending further action from the court.

Reuters contributed to this report