"aren't subpoenas issued by court authorities"
Oh my, let's learn Venn diagrams, shall we:
Courts can issue subpoenas.
Nott all subpoenas are issued by a court.
See how that works.
Here, see if this hepps you:
An administrative subpoena under U.S. law is a subpoena issued by a federal agency without prior judicial oversight. Critics say that administrative subpoena authority is a violation of the Fourth Amendment to the United States Constitution, while proponents say that it provides a valuable investigative tool.
So the executive branch (not a court) can issue a subpoena.
Now, are you STILL trying to claim CONgress is a court?
Are you claiming CONgress can issue injunctions, seize personal assets, order a citizen to a term of years in a Federal prison?
So, what can CONgress do if somebody is held in contempt?
Any idea? Try some guesses.