The National Organization for Marriage (NOM) is calling on Republican Governor Sam Brownback, a strong opponent of marriage equality, to ignore a ruling striking down the state's ban on gay marriage.

Gay and lesbian couples started marrying in Kansas on Thursday, a day after the Supreme Court refused to stay a lower court's ruling declaring the ban invalid.

(Related: Kansas officials fight implementation of gay marriage ruling.)

“These lower court decisions are illegitimate,” NOM President Brian Brown said in a blog post. “They violate the overarching constitutional principle that powers not specifically granted to the federal government are reserved to the states. The US Supreme Court has specifically recognized in the Windsor case that the regulation of marriage has always been a state function, and this remains so. Therefore, we call on Governor Sam Brownback to reject the idea that Kansas must abandon marriage because out of control federal judges say so.”

“The question for the people of Kansas, and indeed the nation, is whether we are going to allow an illegitimate order by federal judges to trump state law and the vote of 70% of the Kansas electorate. Fifty million Americans in over thirty states have voted in support of traditional marriage and it's time that states fight back to protect the decision of those voters,” he added.

The Human Rights Campaign (HRC), the nation's largest LGBT rights advocate, criticized the move.

“So now, instead of continuing to defend these marriage bans in court, NOM has instead decided the best strategy moving forward is for anti-equality governors to simply ignore the federal courts that rule the bans unconstitutional,” the group said. “As it turns out, the U.S. Constitution rather clearly spells out the powers vested in the federal judiciary and nowhere does it say state governors can ignore federal court rulings because they don't like them.”