Generally, that would apply to judges and lawyers. As an officer of the court, I could issue a subpoena in a lawsuit to compel a witness to appear in court, among other things. It has to be related to a case- I couldn't subpoena you outside of that context.
Failing to respond to a subpoena would lead to me going to the judge and asking for a court order- failing to respond to a court order would lead to contempt of court.
My fiance is the litigator in the family- I'm just a transactional lawyer, and she wants me to add the caveat that there may be differences in various jurisdictions as to the extent of the subpoena power.