You miss the point, they can be sued after agreeing to it but not implementing it. For example, let's say Poland agreed to GDPR but they went ahead and made it

You miss the point, they can be sued after agreeing to it but not implementing it. For example, let's say Poland agreed to GDPR but they went ahead and made itself a hub for data brokers with no respect to GDPR, then Poland gets sued and funds cut. Poland doesn't get sued or funds cut if they voted against GDPR and blocking it in first place.