BRUNSWICK — A federal grand jury indicted two Brunswick men in their 70s for allegedly conspiring to defraud the U.S. government of hundreds of thousands of dollars.

David E. Robinson, 75, and F. William Messier, 70, are charged with multiple counts of conspiracy to defraud the U.S. government by impeding or impairing an IRS investigation, according to court documents.

Messier has not filed a federal income tax return since 1997, though the IRS assessed taxes, interest and penalties against him for $172,000 for the years 2000-2004, according to a release issued Aug. 28 by U.S. Attorney Thomas E. Delahanty II.

In addition, Messier allegedly earned more than $390,000 in gross income from renting antenna space on radio communication towers he owns and renting access to his property to customers who built their own communications towers or located electronics equipment on the property, according to Delahanty.

Robinson, who claims to be the “interim attorney general” of the “Maine Republic Free State,” allegedly worked with Messier to thwart the IRS investigation, according to the release.

The indictment charges that, after the IRS sent notices of levy to Messier’s customers, Robinson and Messier took a number of steps beginning in 2012 to obstruct and impede the IRS, including presenting the IRS with a fake and worthless money order for the amount Messier owed and sending threatening and harassing documents to Messier’s customers urging them not to cooperate with the IRS.

Messier faces up to 13 years in prison and fines totaling $1 million if convicted on all counts.

Robinson faces up to five years in prison and a fine of up to $250,000.

An indictment reflects the grand jury’s determination evidence exists to move forward with criminal charges, but it is not a finding of guilt. Both men are scheduled to appear in U.S. District Court in Portland on Sept. 5.