Don't Ask, Don't Tell is
law, not an executive order.
It was a compromise Clinton reached with congress. So unfortunately it isn't just as easy as making a new executive order (I too thought that it was an executive order this morning and was looking for it when I found I was wrong).
ETA: Well, that link apparently doesn't work. Anyway, it was part of HR 2401 in 1993 if you want to seek it out.