Hi,

Before, only premium users that are marked as enemy can join a person's games.

But now, I noticed even standard users that are marked as enemy can join games.

Not sure if this is a bug or if the rules have changed.

I see you are standard member as I am, so you can't block anyone from joining your games, if that's what you mean. Maybe you was premium before so you blocked someone, but when your membership expire you can't stop them anymore.