Sen. Marco Rubio, R-Fla., sent a letter to Attorney General William Barr Monday calling for him to investigate former Secretary of State John Kerry for potential violations of the Logan Act or the Foreign Agents Registration Act.

President Trump had previously called on Kerry to be investigated after it was revealed that Kerry had been in secret talks with the Iranian government in a bid to salvage the Iran nuclear deal after Trump backed out of it.

“As you know, former Secretary Kerry’s actions since leaving office have come under scrutiny as they related to the Iran nuclear deal, known formally as the Joint Comprehensive Plan of Action,” Rubio said in the letter to Barr.

“The American people deserve to know that U.S. laws are enforced regardless of any individual’s past position,” he added. “The Department of Justice should therefore make a determination on whether or not former Secretary of State John F. Kerry’s recent actions related to the Joint Comprehensive Plan of Action with Iran potentially violate the Logan Act or the Foreign Agents Registration Act.”

Rubio previously asked then-Attorney General Jeff Sessions to investigate Kerry in 2018.

Trump said earlier this month that he would like to see the 75-year-old Kerry investigated. The Logan Act forbids unauthorized people from negotiating with foreign governments.

“What I would like to see with Iran, I would like to see them call me. John Kerry, he speaks to them a lot. John Kerry tells them not to call. That is a violation of the Logan Act. And frankly, he should be prosecuted on that,” Trump said.

Kerry served as secretary of state from 2013 to 2017 under President Barack Obama.