The Supreme Court is weighing a challenge to a Cook County ordinance that bans the sale or possession of assault weapons and large-capacity magazines, brought by two Illinois men who say it violates the Second Amendment.

Cook County has asked the justices to dismiss the case if lead plaintiff Cutberto Viramontes is allowed to withdraw, arguing his departure could leave the Court without a live dispute to decide.

Viramontes’ attorneys requested his removal in a brief filing that offered no explanation, raising questions about why he wants to leave a case set for argument next month and how plaintiffs are vetted in high-profile challenges.

Two gun-rights groups are also plaintiffs, but associations generally must identify a member who could establish standing to sue individually.

The other individual plaintiff, Christopher Khaya, wants to buy an IMI Galil, a semi-automatic rifle similar to an AK-47 rather than an AR-15; Cook County says the case record does not show whether it operates like an AR-15 or is commonly used for lawful purposes.

The dispute turns in part on the Supreme Court’s 2022 Bruen decision, which requires modern gun regulations to align with the nation’s historical tradition of firearm regulation; Cook County and Connecticut argue history supports regulating unusually dangerous weapons, while challengers point to the Court’s 2008 protection for weapons in common use and estimate that 20 million to 30 million AR-15-style rifles are in circulation.

Viramontes’ withdrawal may have limited impact on the broader issue because the Supreme Court has also agreed to hear a challenge to Connecticut’s similar ban, and its ruling there would likely affect other bans.

Ten states have enacted similar bans on AR-style rifles, and the Cook County case is one of several Second Amendment disputes reaching the Court after Bruen.