They also can't do business with EU entities, so they're very likely locked out of the EU banking sector. They were already sanctioned in the US, so that leaves them very few banks that will process their payments.
But if they have the support of their home state, even these restrictions won't impact them much. They'll be issued false identities for use abroad, and almost any state would be able to issue an identity which could fool KYC requirements at a bank.
They could not care less. Their own government will never let them have anything in EU.