The U.S. Supreme Court’s expected decision this spring that gay couples have a constitutional right to marry will for most mark the end of a decades-long culture war.

But a small circle of Christian activists aren’t giving up yet — and they are already winning over some Republican presidential candidates to their last-ditch effort. Resting their hopes on an effort to redefine the role of the federal judiciary, the activists’ argument takes on a central tenet of modern American politics: that the Supreme Court has the final say on what is the law of the land.

“There are three branches of government,” Andrew Schlafly, a lawyer and conservative activist, told TIME in an interview. “If the Supreme Court overreaches on an issue, the other two branches are there to check and balance it. The Supreme Court can make that decision, but it can’t enforce its own orders in a state. That’s up to the Legislative and Executive branches.”