* Editor's note: this story has been updated with comments from Empower Texans General Counsel Tony McDonald.

A criminal complaint against Empower Texans, a conservative group that mailed out an attack ad resembling an official government notice that targeted GOP state Rep. Charlie Geren, is “under review” by the Travis County District Attorney’s office, The Texas Tribune has learned.

A person who self-identified as a Tarrant County voter sent a letter to the DA’s office alleging that the group ran afoul of a criminal law that prohibits people from posing as government authorities, correspondence obtained by the Tribune shows. Mindy Montford, Travis County's first assistant district attorney, confirmed that her office had received a complaint about the group on Tuesday.

“It’s under review,” Montford said.

The controversial mailer attacks Geren for his “relationship” with a lobbyist — who happens to be his wife, Mindy Ellmer. What voters see in bold letters when they open the mail piece is “NOTICE,” above a slightly smaller font that says, “Of Relationship With Registered Lobbyist.” Then it lists Ellmer's long list of corporate lobby clients.

The mailer purports to come from the “Texas Ethics Disclosure Board,” an official-sounding name that Empower Texans registered with the Secretary of State's office late last month. There is no such government agency, though there is a Texas Ethics Commission that polices campaign and lobbyist disclosure rules.

The mailer underscores how hard it can be for voters to understand who is sending and funding the political messages they receive. The name "Empower Texans" does not appear on the ad. Nor is there any "paid for" political disclaimer on it. Empower Texans is a non-profit "dark money" group that does not have to disclose its donors.

This controversial mailer is now the subject of a criminal complaint being reviewed by the Travis County DA's office. Empower Texans

Geren said confused voters have asked him about the mailer.

"They're trying to deceive my constituents," said Geren, a top target of the group. The longtime Fort Worth lawmaker, one of outgoing House Speaker Joe Straus' top lieutenants, said the advertisement was designed to look official.

"It looks like it's coming from a state agency and it's not," Geren said. "A guy at church handed it to me and said what is this. I said it's another lie by Empower Texans, and he said, 'Well it looked real.' "

The complaint alleges Empower Texans may have violated a provision of the Texas Penal Code, under section 37.11, which prohibits people from posing as government officials. Specifically, the law says a person commits a third degree felony if he “knowingly purports to exercise any function of a public servant or of a public office, including that of a judge and court, and the position or office through which he purports to exercise a function of a public servant or public office has no lawful existence under the constitution or laws of this state or of the United States.”

Empower Texans General Counsel Tony McDonald said the group had not heard from prosecutors or seen the complaint but he vowed to fight any legal action against the non-profit.

"There's not a chance in hell that we're ever held liable under 37.11," McDonald said. "If we've got to fight it, we'll fight it. We never back down from First Amendment fights, ever." He disputed the idea that voters might find the mailing "deceptive" and said the contents of the ad were truthful.

Earlier, Empower Texans' CEO Michael Quinn Sullivan took to Twitter to respond to queries that the Tribune sent to him via email and voicemail.

"Haha! #TxLege @CharlieGeren doesn't like people finding out about his major conflicts of interest," he said, adding that "Corrupt Charlie" was "working the Travis County DEM district attorney to try to shut us up."

The district attorney's office in Travis County, a liberal stronghold, is in Democratic hands. Sullivan works to get conservative Republicans elected to office.

Geren said he has adhered to all ethics laws related to the disclosure of any potential conflicts of interest involving Ellmer. The longtime Fort Worth incumbent faces a primary challenge from businessman Bo French, one of the top recipients of largesse from Empower Texans' political action committee.