(RNS) Oklahoma’s referendum against state judges considering Islamic law is unconstitutional, the 10th U.S. Circuit Court of Appeals ruled on Tuesday (Jan. 10), upholding a lower court ruling that had blocked the measure.

The ruling could affect more than 20 other states where laws against Shariah are under consideration.

In a 37-page ruling, the 10th Circuit’s three-judge panel dismissed assertions by lawyers for Oklahoma that the law did not discriminate against Muslims.

“That argument conflicts with the amendment’s plain language, which mentions Shariah law in two places,” wrote 10th Circuit Judge Scott Matheson.

The Denver-based judges said that courts should be wary of meddling in voter referendums, but that minorities’ constitutional rights must be protected.

Some 70 percent of Oklahoma voters approved the referendum in November, 2010. Muneer Awad, head of the Oklahoma chapter of the Council of American-Islamic Relations, sued to block the measure, saying it discriminates against Islam and violates church-state separation.

“This is an important reminder that the Constitution is the last line of defense against a rising tide of anti-Muslim bigotry in our society,” Awad said in a statement, according to The Denver Post.

Last year, a U.S. District Court Judge in Oklahoma City also found the ban unconstitutional, and issued a temporary injunction preventing it from taking effect.

The case now returns to the district court in Oklahoma, which is expected to issue a permanent injunction against the law.

If Oklahoma Attorney General Scott Pruitt decides to appeal that case, it would return to the appeals court, and could eventually be heard by the Supreme Court.