I mean, they can keep running. Who's gonna tell them to close down and stop using the name? McD which doesn't do business in Russia?
Btw, there was an infamous Burger King in Pittsburgh that kept running for years without license. They god license taken away because they weren't up to standards, but they didn't bother, and kept selling as Burger King. Once they ran out of actual Burger King products, they just faked it with what they could scavenge elsewhere.
Sorry for linking twitter, but I think it explains it best: https://nitter.net/ohip13/status/1270010175697674241