For purposes of the statute protecting judges from impedance, interference, or intimidation, an immigration judge is a judicial officer who exercises the authority of the Attorney General, and therefore a judicial officer of the United States.
http://media.ca11.uscourts.gov/opinions/pub/files/201710741.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.