'First time in modern history': How the killing of Iran’s Khamenei rewires America’s 'no assassinations' era

Killing Iran’s Supreme Leader marks a seismic shift in US doctrine, from covert coups to open decapitation strikes, with consequences Washington can’t easily control.

• US and Israel killed Iran's Supreme Leader Khamenei in Tehran
• This marks the first open US killing of a sitting foreign leader
• Strike sparks debate on breaking assassination taboo

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For decades, Washington treated assassinating foreign leaders as a line it would not cross.

After Cold War misadventures and CIA scandals, three US presidents, Gerald Ford, Jimmy Carter and Ronald Reagan, signed executive orders banning US involvement in political assassinations. Reagan’s order remains technically in force.

Now, that line appears to have shifted.

According to CNN presidential historian Tim Naftali, the killing of Iran’s Supreme Leader Ali Khamenei marks the first time in modern history that the United States, working openly with Israel, has killed the sitting leader of a foreign state. CNN reported that the operation has effectively opened an undeclared war with Iran.

The Trump administration has avoided the word 'assassination.' Instead, it has framed the strike as a response to what it described as an imminent threat from Tehran, citing Iran’s nuclear ambitions, missile capabilities and support for militant groups.

In a phone call with ABC News, President Donald Trump offered a more personal justification. “I got him before he got me,” Trump said, referring to US intelligence claims in 2024 that Iran had plotted to target him. Iran denied those allegations.

CNN noted that US intelligence agencies had been closely tracking Khamenei’s movements, monitoring where he lived, who he met and where he might retreat in a crisis. The strike reportedly coincided with intelligence suggesting several senior Iranian political and military leaders would be gathered at the same Tehran compound.

A satellite image released after the attack showed smoke rising from the complex.

A long-standing taboo

The United States has been involved in regime change before. But historically, leaders were toppled or prosecuted, not openly targeted and killed by US action.

Iraq’s Saddam Hussein was captured after the 2003 invasion and executed following an Iraqi trial. Libya’s Muammar Gaddafi died during fighting after NATO-backed operations helped rebels seize control.

After World War II, Allied powers prosecuted Nazi leaders at the Nuremberg trials rather than assassinating them.

The CIA’s covert history is more complicated. The agency was secretly involved in the 1973 coup in Chile that led to the death of Salvador Allende. It also backed the 1953 overthrow of Iranian Prime Minister Mohammad Mosaddegh, fearing Tehran’s oil resources might tilt toward Soviet influence. In Vietnam, US complicity preceded the killing of Ngo Dinh Diem.

But these actions were covert and often denied for decades.

The political backlash at home was severe. After Watergate, the bipartisan Church Committee investigated intelligence abuses, documenting multiple failed attempts to kill Cuban leader Fidel Castro. Its findings cemented bipartisan opposition to political assassination.

President John F. Kennedy was quoted in the report warning: “We can’t get into that kind of thing, or we would all be targets.”

Richard Helms, a former CIA director involved in earlier covert operations, testified that removing a foreign leader by force often left the US worse off. “Who is going to take his place,” he asked lawmakers, “and are you essentially better off when it is over than you were before?”

The post-9/11 shift

After the September 11 attacks, Congress granted presidents sweeping authority to use force against terrorist groups. Under that legal framework, US administrations targeted and killed non-state actors, including al-Qaeda leader Osama bin Laden and, under Trump in 2020, Iranian General Qasem Soleimani.

The strike on Khamenei crosses into different territory: the killing of a sitting head of state.

CNN reported that technology has also reshaped the battlefield. Drone surveillance, precision projectiles and real-time intelligence have made targeted strikes more feasible. Israeli forces previously released drone footage showing the final moments of Hamas leader Yahya Sinwar. Iran has alleged that another Hamas figure, Ismail Haniyeh, was killed in Tehran by a short-range projectile last year.

The exact weapon used in the strike on Khamenei remains unclear.

A new geopolitical precedent

Naftali told CNN that while many may not mourn Khamenei, the precedent is profound. Deciding to eliminate a foreign head of state, he argued, is not a choice to be made lightly.

The Reagan-era executive order banning assassinations technically still stands. But Trump has broad immunity for official acts following a recent Supreme Court ruling, and he has not sought fresh congressional authorisation for the operation.

In practical terms, the US has now removed two adversarial leaders overseeing major oil reserves in a matter of months, with Venezuela’s Nicolás Maduro currently facing legal proceedings in New York and Khamenei dead.

The deeper question, raised decades ago by US lawmakers themselves, now returns with force: does eliminating a leader solve the problem, or create a larger one?