The IMMs try to enforce it, but the reality is your imperial character will be a lot more successful and powerful if you take the team evil approach. There has to be some kind of automated mechanic that ties the cabal powers to the designed RP restrictions. Otherwise the RP restrictions won't happen. To my recollection, only one Emperor has been desposed in the history of CF.

For example, the tendency over the last couple years for imperials to complain about "fortlanders" while merrily working together with other imperials from different sects. In many cases, sects should get along worse than outlanders and fortress should.