A federal appeals court declined to reinstate President Donald Trump’s ban on travelers from seven Muslim-majority countries on Thursday, potentially setting the stage for a showdown in the Supreme Court.

A three-judge panel from the 9th Circuit Court of Appeals in San Francisco upheld a lower court’s ruling that initially halted the ban. Enacted by Trump during his first week in office, the ban barred citizens from Iran, Iraq, Libya, Somalia, Sudan, Syria, and Yemen from entering the country, and temporarily halted the resettlement of all refugees in the U.S.

Trump indicated he would appeal the ruling in an all-caps tweet.

Assuming the 9th Circuit’s ruling is appealed, the Supreme Court could eventually decide the issue. The court is still operating with only eight justices, and Trump’s nominee to fill the vacant seat, Judge Neil Gorsuch, won’t be confirmed in time to cast a tie-breaking vote. If the Supreme Court rules 4-4, the lower court’s ruling to halt the ban would remain in place.

The ban was widely criticized for targeting Muslims, and several states sued the Trump administration claiming it harmed citizens, businesses, and universities. Washington state’s lawsuit led to a ruling by U.S. District Court Judge James Robart putting Trump’s order on hold while the issue was sorted out in court. Travel and refugee resettlement was allowed to resume during the interim.