What happens to all those personnel thrown out for being gay? Do the convictions stay as recorded or will there be some way they can have that blemish on their record removed and possibly come back to the military (if they wanted to)?
I’m not sure there’s a GQ answer, because presumably the fate of those previously-discharged soldiers will, in some measure, be determined by how the new law is written.
It is conceivable, on the one hand, that they could write a measure into the law that says something like: “All members of the armed forces previously discharged for homosexuality will have their records cleared and will be permitted, if they desire, to return to active duty.”
On the other hand, it’s just as likely that the law might say something like: “This law goes into effect on [date], and in no way affects the outcome of previous dismissals of homosexuals from the armed forces.”
I guess it’s even possible that the new law wouldn’t mention the old rules at all, which would probably mean that all previous dismissals etc. would stand.
Your question basically asks for speculation about what an as-yet-unformulated change in the law might look like at some indeterminate time in the future, and i don’t think there’s a clear answer.
Nitpick–it would be exceedingly unlikely that a gay servicemember would be discharged via a Dishonorable Discharge, which can only be issued by a general court-martial, and which is the equivalent of a felony conviction. Servicemembers convicted of murder receive Dishonorable Discharges; gay servicemembers do not.
An Honorable Discharge and a Dishonorable Discharge are two ends of a spectrum of discharges from best to worst. Wikipedia describes the different types of discharges here.
More likely, a servicemember discharged for homosexual conduct would receive a General Discharge (under honorable conditions).
Perhaps we can speculate by analogy 
What’s been the situation in other countries that have already let gays into the military?
The particulars may also be part of the political negotiation process. It doesn’t matter what other countries have done. If the only way the law will be passed is to do nothing for those who were already discharged for homosexuality, then that’s what’ll have to happen.
OTOH, if President Obama rescinds DADT by executive order, he can do what he chooses, so all bets are off.
Robin
Pure speculation, but my guess is that those who received a General Discharge may be offered some sort of review process to upgrade their discharge to Honorable.
There is currently a review process in place that can upgrade a problematic discharge. It cannot do anything, though, about a discharge imposed by a court-martial, and the reenlistment code is handled somewhat separately.
I wouldn’t have thought that the President could do that, since DADT is mandated by a law passed by Congress. Doesn’t he have to see that that law is “faithfully executed”?
Wouldn’t the usual policy be that these discharges were conducted under the military regulations that existed at the time of the discharge? If you were an openly gay member of the armed forces in 2008 and it was a violation to be openly gay in 2008, then a law passed in 2009 would have no effect on your discharge.
Not necessarily. My cite pretty conclusively shows that, as soldiers discharged with other than honorable discharges in the 1970s because on failed urinalysis were entitled to a review of the character of their discharge based on a judicial decision since.
There’s a difference though between a court ruling overturning a law and legislative (or executive) repeal. A court ruling like this is essentially saying that the law was invalid even at the time it was in effect. Legislative repeal is essentially saying that something that was illegal is now no longer illegal. But the law at the time was still valid at the time so there’s no automatic overturning of the convictions (or other penalties) that resulted from that law.
My knowledge is out of date, but when I was in gays were getting other than honorable discharges that automatically upgraded to honorable after a year or so, assuming they weren’t convicted of any other “crime.”
There have been gays who have won court cases and been reinstated, so I don’t think it’s unreasonable for the slate to be wiped clean and let the service member rejoin, but just like anyone else who gets out and wants back in, it may well involve losing rank, going back through basic training and more or less doing it all over again.