The man, Mark Sams of Charlo, admitted to the autograph-signing and photo sessions using Noel Haggard's name, but denied accepting money, The (Kalispell, Mont.) Daily Inter Lake reported Tuesday.
When initially questioned about the weekend incident, Sams said his name had been changed as a child for protection, a Ronan police detective said.
An agent for the Haggard family told authorities Sams was not related to the singer.
Police said Sams was arrested on an outstanding Montana warrant and has an arrest warrant from Maryland against him. The case is under investigation and charges are being considered, police said.