Mr. Laser Beam wrote:
There are only two requirements for Federation membership: One world government, and no caste-based discrimination. A world that is ruled by a monarchy would qualify, as long as it satisfied those two things.
Pretty sure there are more requirements then that. A Stalinist dictatorship would not have a caste system, but I do think a poor civil rights record in general would be frowned upon by the Federation.
I doubt the Cardassian Union would be allowed into the Federation, when it was still a military dictatorship. As seen with "The Drumhead" the Federation has some Bill or Charter of Rights and I think a government that hasn't willing to adopt those rights wouldn't be allowed in.