You would think so, but there isn't. Even if it is a child custody case. Even if you have a subpoena. I worked one place that would let you off if you were a witness in a criminal case or had jury duty (because it was law), but never for a civil case. After all, you should have conducted your personal life in such a way that it didn't interfere with work.

Of course, this was a state that didn't require any reason to fire you. Sometimes folks could get unemployment afterwards, sometimes not.