NEED TO KNOW

• Iran signed UNCLOS in 1982 and never ratified, leaving its treaty obligations contested.
• Rubio is invoking "international waterway" rules the U.S. itself never ratified either.
• The real legal fight is whether transit passage is customary law binding non-parties.

WASHINGTON (TDR) — Secretary of State Marco Rubio's demand that the world treat Iran's effective closure of the Strait of Hormuz as a violation of international law rests on a treaty Iran never ratified, and that Washington never ratified either.

The big picture: Cable shorthand calls Hormuz an "international waterway" Iran is illegally blocking. The legal architecture is messier, and both sides exploit the gap.

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• Iran signed UNCLOS in 1982 but never ratified, declining contractual obligations under Part III's transit-passage regime.
• The U.S. also never ratified, with 34 Republican senators opposing accession in the last serious push.
• Oman ratified; the UAE ratified in 2009. The strait's shipping lanes run through Omani waters.

Why it matters: Roughly 20% of seaborne oil and LNG normally moves through the 21-mile passage. Since February 28, tanker traffic has fallen to near zero, with about 1,600 ships and 23,000 sailors stranded.

• Brent crude hit $126; U.S. gasoline crossed $4.50 per gallon.
• Iran's Persian Gulf Strait Authority, stood up May 5, requires "Vessel Information Declarations" for transit.
• The U.S. has blockaded Iranian ports since April 13, mirroring the conduct it condemns.

Driving the news: Rubio took the legal argument to the U.N. Security Council this week, framing it as a test of the institution.

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• "Project Freedom," the U.S. escort operation, lasted 48 hours; only two ships transited before Trump paused it.
• Iran fired on U.S. Navy vessels, struck a UAE-owned ADNOC tanker, and damaged a French-flagged ship transiting without IRGC clearance.
• Trump confirmed the port blockade remains "in full force and effect" during the pause.

What they're saying:

• Marco Rubio, Secretary of State — "Is the world going to accept that Iran now controls an international waterway? What is the world prepared to do about it?"
• Mojtaba Khamenei, Supreme Leader — Called for "using the leverage of closing the strait" to build "a new regional and global order under the strategy of a strong Iran."
• Gene Seroka, Port of Los Angeles Director — "Nothing short of a true peace accord that is demonstrated and proven will gain the confidence of the commercial shipping community."

Yes, but: The administration's legal posture has a hole its critics rarely press. Washington is citing UNCLOS rules it spent 40 years refusing to ratify, while running a port blockade legally indistinguishable from what Iran is doing in the strait.

• Iran's 1982 interpretive declaration said it would extend transit passage only to UNCLOS parties, meaning by Tehran's own rule the U.S. gets the older 1958 innocent-passage regime.
• Washington's answer: UNCLOS reflects customary law that binds everyone. Tehran's answer: persistent objector.

Between the lines: The legal fight isn't whether Iran signed a paper in 1982. It's whether transit passage has hardened into customary international law binding non-parties, and whether Iran's persistent-objector posture survives the test. That's the argument international lawyers have been having for two decades, and it's the one Rubio's Security Council pitch leans on without naming. Both the cable framing of "Iran is breaking international law" and the contrarian framing of "Iran owes nothing to anyone" skip the substantive question. Washington's port blockade cuts the same way: vulnerable under the customary rules it wants enforced in Hormuz, defensible only under the wartime self-defense carve-outs Iran is invoking too.

What's next:

• Pakistan-mediated talks continue; Trump's pause of Project Freedom is contingent on a finalized agreement.
• The U.S.-led Security Council resolution faces probable Russian and Chinese objection.
• Insurers are watching whether PGSA compliance becomes a sanctions trigger under OFAC's May 1 advisory.

If "international waterway" means anything, does it mean the same thing when the country invoking it is also blockading its adversary's ports?

Sources

This report was compiled using reporting from NPR, CBS News, CNN, NBC News, Fox News, The Washington Institute, and the American Society of International Law.

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