Can an employer fire you and take back vacation pay out of your check

IF you had consented in advance to them deducting any amounts you owed, such as for vacation you had taken but not accrued, this would be legal. Such consent could be your specific agreement to them doing this now, or it could be inferred from you continuing to work there and take vacation after having been made aware that this was the policy (to continue employment or use vacation after being told what the rules about vacation are shows agreement to those rules).
However, if you never consented to the deduction, they could not do this: the law is very clear that employers may not withold or deduct employee pay without employee consent (or a court order, such as court-ordered wage garnishment). In theory, you could sue for the money; in practice, if they took out the correct amount (did not overwithhold), there's no point to legal action, since if you owe them for unaccrued vacation, they could interpose that amount as a set-off against any amounts they owe you and you will net out to the same place as you are now: when you sue someone for $X, if you legitimately owe them $Y, they can raise you debt to them in the lawsuit and seek an offset against what they owe you, so that $X = $Y, the two amount cancel out.