As type certificate holders for the An-124, the Ukranian company can certainly stop the type from flying by withdrawing said certificate. But the fact that this is going through the courts implies that normal communication lines are not being used, and it may be more of a political action than an airworthiness related one. The type most likely is seen as a strategic asset by the Russian side, and it wouldn't surprise me to find out that they have taken steps to 'disconnect' the Russian operation from any Ukranian influence, as is implied by the original article linked to in the thread that atakacs referenced.