U.S. District Court Judge Matthew Kacsmaryk blocked the Bureau of Alcohol, Tobacco, Firearms and Explosives from enforcing its ban on AR-15 style “pistols” equipped with arm braces, calling the agency’s new rule unlawful.

“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.

[It’s not clear whether this is a TRO or a final ruling. If it’s the latter, get ready for an appeal, but I’d rather be on this side of an appeal than the other. There are an estimated 40 million qualifying firearms in use, which would make this clearly fall under the “commonly held” standard set by SCOTUS, not to mention issues of ex post facto enforcement. — Ed]