The U.S. Department of Justice has opened a new front in the national fight over firearms regulation, filing suit on July 1 against California to block enforcement of the state’s newly enacted “Glock Ban” and to challenge the California Handgun Roster under the Second Amendment. The case is notable not just for its subject matter, but for the posture: the federal government is now directly attacking one of the country’s most developed state-level handgun regulatory systems.

At a high level, the lawsuit appears aimed at two pillars of California firearms law.

The Supreme Court on June 18 narrowed how the federal government may apply the firearms ban covering “unlawful users” of controlled substances, rejecting a broader theory that could have swept in a wide range of gun owners, including some marijuana users. The ruling is likely to become a significant reference point in Second Amendment litigation because it addresses how closely firearm restrictions must fit the government’s asserted public-safety rationale.

At issue was the federal statute that bars certain drug users from possessing firearms.

The U.S. Supreme Court closed out a closely watched cross-border liability fight this week by unanimously rejecting Mexico’s effort to hold American gun manufacturers responsible for firearm trafficking and cartel violence south of the border.