At least seek out a free mini consultation from a lawyer who handles labor law.

With most companies, employees accrue paid time off for vacations, sick time, etc. at a rate of a certain amount of PTO for hours clocked at work. Because they can estimate how many hours of PTO you will earn in the year, many companies allow you to take vacation time up to your expected accrual amount before you've actually accrued it, knowing that you will continue to accrue it as you work throughout the year. If the company allows you to take paid vacation time before you actually "earn" it then I believe it's standard practice for them to take the money you were paid for any hours of PTO that you did not accrue before your termination out of your final check. It's worth checking with a lawyer, but I believe they are within their rights to do this, since they paid you essentially in advance for time you didn't earn. Worth checking since I could be wrong, but this is my understanding.