
Quoting
Mr. Knowitall
Your employer may not discipline you for complying with a subpoena, but your employer does not have to pay you for the time you miss from work.
If you have accrued vacation time sufficient to cover the missed day, and are otherwise entitled to obtain vacation time for that day consistent with your employer's requirements for requesting and scheduling vacation, then your employer should follow its policies and allow you to take the vacation day -- to do otherwise would be reasonably characterized as penalizing you for observing the subpoena.