No in MOST states they can marry any consenting adult of the opposite sex, just like every one else. That is due process and equal treatment under the law. You want something else, give it a name and sell it to the state legislatures. You also might want to check out the difference between a simple mental disorder and true insanity.
Things are getting twisted here.
People are suggesting that homosexuality is a "mental disorder" which can therefore prevent gay from marrying in the same way an insane person can be prevented from marrying or having many other rights others have.
The second point is equal treatment under the law. The US Supreme Court said separation is not equal. Back in the day similar arguments were being used to keep black people down, now they're being used to keep gay people down.
It's about being able to choose who you want to marry. The US govt doesn't tell straight people who they can marry or not. They say they can choose whoever they like, black or white or yellow, old or young (over the age of consent of course).
Why do you think it's acceptable for the law to decide for people who they can choose to marry when the people are consenting?
This is the issue.
Are you free or are you at the whim of the government?
Most people will say liberty and freedom are the most important things and then turn around and say "for me, not for them".
Hypocrisy? Of course.
As for the difference between mental disorders and insanity, well hell, someone in my family suffers from bad mental disorders and SHE'S MARRIED.