Also, when you play someone with mixed rules, you may abolish rules,

i.e. when the other players says something along the lines of, "hey, you have rules from -whatever-, let's use them too."

After the game of mixed rules, whether you win, lose or draw, one of three things may happen.

1. Nothing, game continues.
2. Rules you are carrying are spread in the region
3. An existing rule in the region is abolished.

It's kinda risky because you might end up spreading rules everywhere and possibly abolish Open. This will most likely happen after you come back from the Lunar Base.

You can remedy this by saving, playing and resetting until you get the desired effect. Note that abolishing a rule is very hard to do and you will most likely end up spreading a rule instead, so be prepared for a lot of resetting.