President Donald Trump tweeted Monday morning that former Obama Secretary of State John Kerry might be in “big violation” of the Logan Act over his talks with Iran.

Trump’s tweet came after his administration announced Monday that they were ending sanctions waivers for Iranian crude oil in an effort to increase economic pressure on the Islamic state. (RELATED: Trump Slaps Iran With Historic Sanctions)

“Saudi Arabia and others in OPEC will more than make up the Oil Flow difference in our now Full Sanctions on Iranian Oil. Iran is being given VERY BAD advice by [Kerry] and people who helped him lead the U.S. into the very bad Iran Nuclear Deal. Big violation of Logan Act?” Trump said on Twitter.

Kerry helped negotiate the contentious Iran nuclear deal, popularly known as the “Iran deal,” with the long-time U.S. adversary in 2015 and has sought to defend the deal’s legacy in the years since he left office. The Trump administration officially pulled out of the deal last year, with Trump calling it a “horrible deal that should never, ever have been made.”

After pulling out of the deal, the administration released a list of demands, including urging the Iranian regime to stop all proliferation and end its support for terrorist organizations such as Hezbollah, Hamas and Al Qaeda.

Kerry responded to the decision by claiming that it “weakens our security, breaks America’s word, isolates us from our European allies, puts Israel at greater risk, empowers Iran’s hardliners, and reduces our global leverage to address Tehran’s misbehavior.”

Last year, Kerry reportedly had discussions with Iranian officials and several world leaders in an attempt to salvage the deal, leading some to suggest that the former Secretary of State was in violation of the Logan Act. (RELATED: Rubio Wants DOJ Investigation Into Kerry’s Iran Meddling)

The Logan Act was signed into law by President John Adams at the genesis of the Republic in 1799. The Act prohibits “private correspondence with foreign governments,” and states that U.S. citizens cannot “directly or indirectly” have any “correspondence” with a foreign government in relation to any dispute with the United States.

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