I always wondered this I figured this would be the best place to ask. Let's say there is a marriage of a guy and girl. One of them decide to get a sex change. Would they still have a legal marriage if they got married and lived in a state banning gay marriage? I've asked my friends and some say that it would still be legal but those were all just guesses.
Depends on the state, and it might surprise you. Texas refuses to recognize changes in birth certificates and found themselves in the odd position of allowing a marriage between a transsexual woman and another woman because they saw them as "man and woman". The federal government deported my friend Sonja because she she is a non-op transsexual; her TS girlfriend tried to marry her and Homeland Security said "no dice". Weirdly, Social Security and the Feds will recognize a sex change on a passport for Post-ops, but not preops, even with all other legal name changes. I guess to answer your question, it depends on how vigilant the authorities are in that state about granting a marriage license; in other words, will they accept the forms of ID offered without "research"? hope that's kinda helpful.
I know your question was about the US, but I believe that in the UK, according to the Gender Recognition Act 2004, people can apply for legal recognition in their new gender - such recognition means that the individual can marry in their new gender. ie. someone born a woman who gets legal recognition as a man can marry a woman. However, if a born-man and born-woman are married, and one undergoes a sex change, and they gain legal recognition for it, their marriage is dissolved and they can form a civil partnership instead. For info on UK law which gives info on gender recognition certificates and issues such as marriage and civil partnerships see http://www.grp.gov.uk/index.htm
