Supreme Court Justice Clarence Thomas signaled he is ready to overrule another judge in a key firearms case on Tuesday.

The Supreme Court on Tuesday denied certiorari to a challenge to an Illinois ban on the sale or possession of assault weapons. Plaintiffs in several cases are arguing the ban violates the Second Amendment of the Constitution, which gun rights advocates say provides for the rights of U.S. citizens to carry firearms. However, Illinois Attorney General Kwame Raoul argued that the Second Amendment does not extend to military-grade weapons.

Prior to Tuesday's decision, the 7th Circuit Court of Appeals denied the petitioners' request for a preliminary injunction, agreeing that the AR-15 is not protected by the Second Amendment. The Supreme Court declined to intervene, as proceedings are still ongoing and the appeals court has not formally upheld the Illinois ban.

Only Justice Samuel Alito would have granted the petition for writs of certiorari in the case. The conservative-tilting court has been viewed as favorable to gun rights, rejecting firearms regulations such as a ban on bump stocks.

Justice Thomas, viewed as among the most conservative justices on the bench, wrote a statement addressing why he agrees the court should not have picked up the case at this point, but argued the court should intervene if the appeals court ultimately upholds Illinois' law.

He wrote that he agrees with the court's wariness "of taking cases in an interlocutory posture" but hopes the court will eventually "consider the important issues presented by these petitions after the cases reach final judgment." Thomas noted the Supreme Court has not addressed which types of weapons are protected by the Second Amendment.

"The Seventh Circuit's decision illustrates why this Court must provide more guidance on which weapons the Second Amendment covers," Thomas wrote. "By contorting what little guidance our precedents provide, the Seventh Circuit concluded that the Second Amendment does not protect 'militaristic' weapons...It then tautologically defined 'militaristic' weapons as those 'that may be reserved for military use.'"

He concluded the court should revisit the case pending its final judgment.

"But, if the Seventh Circuit ultimately allows Illinois to ban America's most common civilian rifle, we can—and should—review that decision once the cases reach a final judgment," Thomas wrote.

David Sigale, the attorney representing plaintiffs in one of the challenges, Harrel v. Raoul, responded to the decision in a statement to Newsweek.

"We are disappointed the Supreme Court will not address the Seventh Circuit's erroneous standard of Second Amendment analysis at this time. However, we will continue to pursue this matter through the upcoming trial on the merits in the District Court, and, if need be, will address the Seventh Circuit and Supreme Court again on the important issues presented in our case," he said.

Newsweek reached out to the Illinois attorney general's office for comment via email.