I am a full time medical transcriptionist and work on a production basis. There are times when there is no work available due to a holiday or there being not enough work to go around. I used to be able to be released from work without pay when that happened. Now my company says I have to cover lost hours by using PTO.
Employment / Labor Attorney
Yes, the employer may dictate the rules for its vacation or PTO program.
If you don't have a promise in a handbook or document from your employer as to PTO rights, then this PTO benefit can be applied as the employer desires. Look to see if you have any promises made on that. There does need to be consistency. It would raise questions if it was not applied to everyone in the same manner. Sucha benefit is not normally a vested benefit and can be changed by the employer.
More facts need to be known so do not rely on comments here until consuting with an attorney that practices regularly in this area of law.