HRS §803-17
When federal marshals can arrest without a warrant
This section lets U.S. marshals and deputy marshals arrest someone without a warrant, but only while on duty, in certain situations, and after their office confirms they are trained. It covers crimes involving physical harm, crimes they believe happened, or when they are told a warrant exists.
The statute, as written — United States marshal or deputy United States marshal; arrest powers
A United States marshal or deputy United States marshal, without a warrant, may arrest a person if: (1) The marshal or deputy marshal is on duty; (2) One or more of the following situations exists: (A) The person commits an assault or other crime involving physical harm, defined and punishable under chapter 707, against the marshal or deputy marshal or against any other person in the presence of the marshal or deputy marshal; (B) The marshal or deputy marshal has probable cause to believe that a crime as provided in subparagraph (A) has been committed and has probable cause to believe that the person to be arrested has committed the crime; or (C) The marshal or deputy marshal has received information by written, telegraphic, telephonic, radio, or other authoritative source that a law enforcement officer holds a warrant for the person's arrest; and (3) The head of the Hawaii district office for the United States [Marshals] Service certifies to the State that the marshal or deputy marshal has received proper training within the agency to enable that officer to enforce or administer this section.
LawTrove is not legal advice. The summary above is a computer-generated restatement — the authoritative text is the official version linked above.