The Supreme Court will begin its annual term hearing Suncor v. Boulder County, a case on whether cities may sue oil companies over climate change. Justice Samuel Alito has recused himself, raising the possibility of a 4-4 split. A deadlock would leave in place a Colorado Supreme Court ruling that Boulder’s claims against Suncor and Exxon Mobil are not preempted by federal law, potentially spurring more climate lawfare.

The clerk didn’t specify grounds for Alito’s recusal. Partisan actors now try to force Justices off cases, but refusing such calls has a long tradition. Justice William Rehnquist wrote in 1972, “A federal judge has a duty to sit where not disqualified.” Justice Antonin Scalia echoed this in 2004, saying folding under pressure invites “increasingly silly” demands.

Groups like Earthworks and Feminist Majority urged Alito to recuse, citing investments in oil companies like Conoco Phillips and a Vanguard fund holding Exxon. The Court previously said Alito lacked direct financial interest. What changed is unclear, but the loss is one-ninth of the Court, risking a deadlock.