In the game settings, you can now enable private lobbies. Friends will not be able to join such a lobby and thats sucks.
In the future, i may implement password to join, which you can also set in the settings, but for now, my attempts have hit a dead end in the final stage.
I understand how important this is, as I know there are cheaters who can spoil your cinema experience, or just unpleasant individuals. But for now, I can only offer kicks.