Since the post-9/11 enactment of the Homeland Security Act of 2002, resulting in the amendment of the IG Act of 1978, Section 6e, most presidentially appointed IG special agents have had full law enforcement authority to carry firearms, make arrests, and execute search warrants. Prior to this time, most presidentially appointed IG and some designated IG special agents had the equivalent law enforcement authorities as a result of other statutes or annually required deputation by the U.S. Marshals Service. The 2002 amendment to the IG Act of 1978 made most deputation of presidentially appointed IG special agents unnecessary. Some designated IG special agents, however, still have full law enforcement authority today by virtue of this continued deputation. Some OIGs employ no criminal investigators and rely solely on administrative investigators, auditors, and inspectors.
https:// en.m.wikipedia.org/wiki/Office_of_Inspector_General_(United_States)