Former Minnesota State Sen. Justin Eichorn has filed a motion to dismiss a federal charge stemming from an arrest in an underage prostitution sting earlier this year, with his legal team arguing he is being targeted by "selective prosecution."

Justin Eichorn, a Republican who represented a district in St. Louis County before his resignation in March, faces a federal charge of attempted coercion or enticement of a minor. In March, he was arrested as part of an online prostitution sting.

In newly filed court documents, Eichorn's legal team argues that the indictment "should be dismissed because the Government's decision to charge Mr. Eichorn in the present indictment was vindictively motivated by personal animus against Mr. Eichorn."

Eichorn's lawyers added, as Eichorn was a public office holder, they believe the indictment to be "vindictive in that it was motivated solely by the fact that the government is unable to secure a more significant period of incarceration for Mr. Eichorn in the initial prosecution by the Hennepin County Attorney's Office."

Documents allege he "intentionally hired or offered or agreed to hire an individual who [he] believes to be under the age of 18 years, but at least 16 years of age, to engage in sexual penetration or sexual contact."

The complaint says he was communicating with undercover officers, who said they began receiving messages from Eichorn and asked for pictures multiple times, including "a naught [sic] pic of you to show me your [sic] real." Eichorn allegedly arranged to meet with the girl in Bloomington, which is where he was arrested.

After his arrest, Republicans and Democrats in both chambers of the state legislature called for his resignation. Eichorn's former district is now being represented by Republican Sen. Keri Heintzeman following her special election win.

Anthony Bettin contributed to this report.

• Prostitution