SPRINGFIELD — A downstate lawmaker whose challenge of Illinois' semiautomatic weapons ban lost at the state Supreme Court earlier this year has petitioned the U.S. Supreme Court to review that decision. 

State Rep. Dan Caulkins, R-Decatur, filed the request with the nation's highest court last week, arguing that the Illinois Supreme Court's 4-3 ruling upholding the ban, issued in August, denied plaintiffs their due process right to a fair hearing due to the participation of two justices with perceived conflicts.

Justices Mary Kay O'Brien and Elizabeth Rochford, both Democrats elected to the state's high court in 2022, received $500,000 from Gov. J.B. Pritzker's campaign and $500,000 from Pritzker's personal trust during the campaign.

The pair also received endorsements from gun control lobbying groups Gun Violence Prevention PAC and Giffords PAC.

"Given the size of the campaign contributions and who gave the contributions, there not only is a question of fairness and impartiality, there also is a question of the independence of the Justices which calls into question the validity of the state court decision," Caulkins said. 

Lawmakers passed and Pritzker signed the legislation banning semiautomatic weapons and high-capacity magazines in January. It took effect immediately, making Illinois the ninth state in the country with a ban on the books.

It was quickly challenged in state and federal court.

O'Brien and Rochford both declined to recuse themselves from the case.

Rochford ended up writing the majority opinion, which dismissed Caulkins' claims that the ban constituted special legislation and denied equal protection to members of the public who weren't classified as exempt from it.

O'Brien, however, dissented, ultimately siding with Caulkins in his claim that the legislation in question violates the special legislation provision in the state constitution.

Caulkins' cert petition — or request that the high court take the case — has been placed on Supreme Court's docket. The Pritzker administration has until Dec. 14 to respond if it wishes to do so. A decision will likely be made next year.

"The Protect Illinois Communities Act is a commonsense law that will remove weapons of war from our streets," said Pritzker spokesman Alex Gough. "It has already been upheld before both state and federal courts, but it's not surprising that Rep. Caulkins and the gun lobby continue to put their extreme ideology over the safety of Illinoisans."

Gough referred questions about whether the state will file a response to Attorney General Kwame Raoul's office, which could not be immediately reached for comment.