Two Brunswick men accused of a tax fraud conspiracy for trying to obstruct and impede the Internal Revenue Service have been indicted by a federal grand jury in Portland.

The indictment against F. William Messier, 70, and David E. Robinson, 75, had been brought against them in June in U.S. District Court in Portland but remained under seal by a judge’s order until Wednesday.

Messier and Robinson are the authors of the book, “Maine Lawsuit Against The IRS: For Unfair Trade Practices,” published in 2012.

The men have each been issued a summons to appear in court on Sept. 5 to face the charges against them.

Messier faces seven charges – one count of corruptly endeavoring to obstruct administration of the tax law, one count of conspiracy and five counts of willful failure to file federal income tax returns.

Robinson faces a single count of conspiracy.

Messier is accused of failing to file a federal income tax return since 1997. In 2012, the IRS began a collection action against him for back taxes, interest and penalties for the years of 2000 to 2004 totaling $172,000. From 2006 to 2012, Messier received a total gross income that totaled about $677,000, according the nine-page indictment.

Messier earned more than half of that 2006 to 2012 income from renting antennae space on radio communication towers that he owned on his Tower Lane property and by renting access to his property to customers who constructed their own communications towers or located electronic equipment on the property, according to the U.S. Attorney’s Office.

Robinson allegedly claimed to be the “Interim Attorney General” of the “Maine Republic Free State,” and urged people not to pay their state and federal taxes, according to the indictment.

“It was part of the conspiracy that the defendants, F. William Messier and David Everett Robinson mailed false and frivolous documents to employees of the IRS,” the indictment states. “(Messier and Robinson) mailed harassing and false documents to customers threatening them to not comply with the IRS collection efforts.”

Prosecutors had initially asked in June that the indictment against Messier and Robinson be temporarily sealed until they could decide whether to seek arrest warrants or issue summonses, according to court records.

If convicted, Messier faces up to 13 years in prison and fines totaling $1 million..

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