Justice Samuel Alito will sit out Monday's opening argument in the Boulder climate case, and he has not said why. On Sept. 28, Clerk of Court Scott Harris sent the lawyers a brief letter saying Alito "will not continue to participate" in Suncor Energy v. Boulder County, SCOTUSblog and Colorado Public Radio reported. That was months after the Court agreed to hear the case.

SCOTUSblog noted that Alito owns stock in oil and gas companies. Federal law tells judges to step aside when they have a financial interest in a party. Justices often list the reason when they recuse, but they are not required to.

The timing matters. With Alito out, a 4-4 tie would leave the Colorado Supreme Court's ruling in place, letting Boulder's suit against ExxonMobil and Suncor move ahead. The Washington Examiner has written that the case could limit states' power to sue oil and gas firms, so the outcome reaches well past Colorado.

Recusal at the Supreme Court works differently than in lower courts. Each justice decides alone whether to step aside, and there is no appeal. In lower courts, another judge can review the choice. When a justice leaves a case, no one can fill the seat, so ties become possible.

The Court adopted its first written code of conduct in November 2023, after reports about gifts and travel given to some justices. Critics said the code lacked a way to enforce it. Supporters said the justices were right to keep control over their own conduct to protect judicial independence.

Alito has been at the center of past debates over recusal. He declined calls to step aside from some cases tied to the 2020 election.

For Boulder, the recusal could help. For the companies, it means they must win five of eight votes.

What we know: Alito is out, and the Court has not said why.
What we don't: Whether the Court will rule 4-4 or reach a majority.