Ukraine is back at the hockey World Championship after 20 years. A ruling in Russia’s favor could knock it out before the tournament begins.

The Court of Arbitration for Sport (CAS) has ordered the International Ice Hockey Federation (IIHF) to allow Russia’s national teams to return to international tournaments immediately. The ruling surprised everyone — including the Russian team itself. It is not even clear how to carry it out in practice, since the fields for this season’s major tournaments were finalized long ago. If Russia is allowed to compete in the upcoming world championship, organizers may well have to drop the lowest-ranked team: Ukraine.