US Sinks Iranian Warship in International Waters

Attack raises questions about legality of ongoing conflict with Iran

Published on Mar. 6, 2026

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The U.S. Navy has sunk an Iranian warship in the Indian Ocean, thousands of miles from the main theater of the ongoing conflict between the two countries. The attack, which took place in international waters off the coast of Sri Lanka, has raised questions about the legality of the U.S. actions under the rules of war, as Congress has not formally declared war on Iran.

Why it matters

The sinking of the Iranian ship in international waters highlights the ambiguous legal status of the growing conflict between the U.S. and Iran, which has involved more than a dozen countries. Experts say a formal declaration of war by Congress is needed to provide a clear legal framework for U.S. military actions against Iran, which have expanded beyond the Persian Gulf region.

The details

The U.S. submarine strike sank the Iranian warship, which was in the Indian Ocean in international waters off Sri Lanka. Military law experts say the Iranian ship would have been a lawful target had the U.S. declared war, but the lack of a formal declaration makes the legality of the attack a murky issue. Iranian officials have condemned the attack as an "atrocity" and warned the U.S. will "come to bitterly regret" the precedent it has set.

  • The submarine strike occurred on Tuesday, March 1, 2026.
  • On Thursday, the House of Representatives voted against a war powers resolution, while a similar measure failed in the Senate on Wednesday.

The players

Abbas Araghchi

Iranian Foreign Minister who called the attack an "atrocity" and warned the U.S. will "come to bitterly regret" the precedent it has set.

Rachel VanLandingham

Retired Lt. Col. and former judge advocate general in the U.S. Air Force, who said the attack "underscores why Congress should have approved this in the first place" because the conflict is expanding beyond the Middle East.

Brian Finucane

Former attorney-adviser at the U.S. State Department from 2011 to 2021, who said the submarine attack would have been lawful if the conflict was authorized by Congress.

Donald Trump

The U.S. President who has said Iran posed an imminent threat, though senior officials in his administration have refrained from calling the conflict a "war."

Marco Rubio

U.S. Secretary who said the threat from Iran became more imminent because Israel planned to strike Iran and Iran would retaliate against Israel and the U.S.

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What they’re saying

“The U.S. will come to bitterly regret precedent it has set.”

— Abbas Araghchi, Iranian Foreign Minister

“When you're going to have such global implications — that's one of the reasons the founding fathers said Congress gets to decide wars of choice.”

— Rachel VanLandingham, Retired Lt. Col. and former judge advocate general in the U.S. Air Force

“The fundamental legal problems under both U.S. and international law of the submarine engagement relate to the underlying use of force in this war against Iran.”

— Brian Finucane, Former attorney-adviser at the U.S. State Department

What’s next

The House and Senate will continue to debate the need for a formal declaration of war against Iran as the conflict escalates.

The takeaway

The sinking of the Iranian warship in international waters underscores the legal ambiguity surrounding the ongoing U.S.-Iran conflict, highlighting the need for Congress to formally authorize the use of military force to provide a clear legal framework for such actions.