From The Truth About Guns:

In the real world, FPC and Mountain States Legal Foundation have teamed up to sue the ATF and DOJ for rewriting federal law. These agencies are changing decades of precedent individuals, companies, and the industry have all relied on through an “agency rulemaking” that does an end-run around Congress. All because the president couldn’t get Congress to pass a law that he campaigned on that would tread upon millions of people’s rights.