“Public safety concerns must be addressed in ways that are lawful. This rule is not,” said the Trump-appointed judge.

The nine-page decision is the latest to challenge the ATF over its rule requiring millions of owners of braced guns to register the firearms and pay a $200 tax, or face 10 years in jail. Kacsmaryk’s decision is the most sweeping, covering the whole country.

At issue is the ATF’s rule issued earlier this year to ban the braces on the guns. The agency claims it turns a pistol into a dangerous rifle and supporters have cited how the weapons have been used in a handful of mass shootings.

However, for years before its ban, the ATF allowed the braces to be sold, and they have become so common that some estimate 40 million or more are in circulation, making the AR-style pistol one of the most commonly held firearms in the nation.

Since the ATF changed its view of the brace and issued its rule, a handful of courts have challenged the agency and questioned how it can overnight make millions of owners potential criminals.

Challenges have been filed in several courts. The one Kacsmaryk ruled on was brought by the Wisconsin Institute for Law & Liberty on behalf of three veterans.