Friends with Citizenship refers to a person from any country, meaninglessly marrying someone from another country, just so that they can become a citizen of that country.
Friends with Citizenship is closely related to Friends with Benefits.
Ted: Hey Bill, Did you see Franks new wife?
Bill: YEAH! She is way hot, how did he find an attractive woman? He looks like a pittbull.
Ted: I guess they met on the internet and got married a week later.
Bill: WAIT A MINUTE! Sounds like Friends with Citizenship!
Ted: What's that?
Bill: Thats when hott chicks get on dating websites, and they find ugly pitbull looking guys to marry so that they can become a citizen of another country.
Ted: Wow! This Example is long!!
Bill: Yeah... lets smoke a joint!