Re: This could get all rather interesting ..
It's the idea of retrospectively and unilaterally adjusting an agreement with the EC without any discussion or negotiation. If you want to derive the benefits of a membership (whatever they are) you must also follow the terms under which you were offered such membership or you may end up with problems.
I am not sure what sanctions can be applied to Russia, but I suspect suspending EU membership could be a possible answer which would have all sorts of unpleasant side effects.