Under the common law practises related to international recognition of foreign marriage, there are a couple of critera that usually need to be met.

First, each party to the marriage must have had the capacity to marry under their respective lex domicilis (the law of the place of their respective domiciles). And then the marriage must have been celebrated according to the formalities imposed by the lex loci celebrationis (the law of the place where the marriage is celebrated). (with thanks to AC*SE in Air Canada forum)

Basically, if both parties are from jurisdictions which permit gay marriage, then the marriage should be recognized as valid internationally. Unfortunately, since the UK does not recognize same sex marriage, visiting British tourists would not be legally recognized in the UK as married when they return.

Buddyboy aka Mike aka "just a simple law student who still thinks a tort is a kind of cake or a girl you don't bring home to meet mother"