Rubio’s letter to Attorney General Jeff Sessions asks the Department to rule on whether Kerry’s meetings violated federal laws including the Logan Act, which bans unauthorized individuals from negotiating with foreign governments, and the Foreign Agents Registration Act, which requires anyone acting on behalf of a foreign government to disclose their interests.

Rubio wrote: “As you know, the Islamic Republic of Iran remains a US-designated state sponsor of terrorism, and the State Department continues to characterize the regime in Tehran as ‘the foremost biggest state sponsor of terrorism’ in its annual reports on international terror.

The American people deserve to know that US laws are enforced, regardless of any individual’s past position.”

He also suggested that Kerry’s actions were an attempt “to lobby and unofficially negotiate with officials in the United States and in foreign governments”, citing a Boston Globe article in May that said Kerry was working behind the scenes to save the Iran deal.

Kerry said that he has had several meetings with Iranian Foreign Minister Mohammad Javad Zarif, since the end of his tenure as Secretary and implied that he told Iran not to make any major strategic changes until Trump left office.

Rubio’s letter follows current Secretary of State Mike Pompeo’s comments on Friday, when he labelled Kerry’s meetings “beyond inappropriate”.

He said: “I am reasonably confident that he was not there in support of US policy with respect to the Islamic Republic of Iran. Actively undermining US policy as a former secretary of state is literally unheard of.”

Trump also criticised Kerry’s meetings in a tweet, which read: “John Kerry had illegal meetings with the very hostile Iranian Regime, which can only serve to undercut our great work to the detriment of the American people.

He told them to wait out the Trump Administration! Was he registered under the Foreign Agents Registration Act? BAD!”
Matt Summers, a spokesman for the former secretary, said on Friday that Kerry’s meetings were hardly unusual or unprecedented.

The problem with that is that no matter how usual it is for former diplomats to meet with foreign leaders, Kerry’s meetings with the Iranian Regime still legitimises a rogue state at a time when its people are pouring into the streets and calling for regime change.