Impersonating a Starfleet officer

Jack, Patrick and Lauren impersonate Starfleet officers

The crime of impersonating a Starfleet officer is the act of purporting to be a member of Starfleet and acting in its name when one is not actually so. This can include wearing a Starfleet uniform in public, issuing orders to legitimate Starfleet officers, or conducting activities while claiming that they are on behalf of Starfleet or the Federation.

In 2368, a Satarran using the alias of Kieran MacDuff posed as the executive officer of the USS Enterprise-D as part of an attempt to use the starship to destroy the Lysian Central Command. (TNG: "Conundrum")

In 2375, the genetically engineered Humans Jack, Patrick, and Lauren were all charged with impersonating Starfleet officers after they brought Sarina Douglas to Deep Space 9, during which they wore Starfleet uniforms and ordered others such as Nog to contact Julian Bashir. Patrick was dressed as an admiral, Jack as an operations officer, and Lauren as a science officer. Whenever they were questioned about their activities, Patrick answered "That's a stupid question!", which succeeded in continuing the deception. Because they were only trying to get assistance for Sarina, Bashir convinced Benjamin Sisko to ask that the charges be dropped. (DS9: "Chrysalis")

The following year, the crew of the USS Voyager discovered con artists Dala, Mobar, and Zar impersonating officers Kathryn Janeway, Tuvok, and Chakotay, respectively. They were able to do so after deceiving Neelix and Tom Paris into allowing them onto the Delta Flyer to steal their database and the knowledge of Starfleet within it. After being captured by the Voyager crew, they were turned over to local authorities for prosecution of their thefts and other crimes. (VOY: "Live Fast and Prosper")