Which begs the question, how could Amram “re-marry” Yocheved if he may have had the din of a Cohen?
You could also ask how he could marry his aunt or remarry a woman who married another man in the interim.
The answer to all such questions is that the mitzvos were not yet given — including the mitzvah against marrying an aunt, remarrying your divorcee or a Kohen marrying a divorcee.
The Wolf