Is there a way to make a mod that changes/disables certain game rules? Such as disabling cultural assimilation, or imposing those United Planet laws by default.
You can turn off cultural conquest as an option at the start of a game.
You can _get rid of_ UP issues by renaming the directory until you want them back, but I'm not sure how you'd impose laws. I suppose you could move the laws you don't want brought up into another directory. That way the only UP issues that come up are the ones you want in the game, but there's no guarantee they'll be implemented.