This is one of the somewhat controversial methods that may work for some and not for others, and is probably in limited supply too, at least if you're considering only liberty supporters for your partner.

Basically, the idea is to marry to move, and nothing more, unless you want it to be more. This is for people who don't believe government's endorsement of marriage has any particular significance on the implied relationship between two people itself and see it as only a kind of a contract between two people. In this case you would use the government's legal institution of marriage because that would give you the legal right to immigrate, but wouldn't necessarily have the exact contract with the partner that marriage usually implies (that is, you wouldn't necessarily make a "real" pledge of love for the rest of your life and those kinds of things). Of course, if you can make it look like a real marriage, at least when someone from government is watching, that would probably be beneficial.

According to Childe Folly on FSP forums, this works for most people who can do it, but not necessarily always.

There's also a discussion of this topic called "Marry A Foreigner For Freedom!".