Do the US and the UK have the right to attack Houthis?

Question

The UN security council demanded an immediate end to Houthis attacks.

Does this give the right to the US and the UK to unilaterally decide to attack Houthis according to UN treaties and/or international laws?

Answer 1

They have the right to use force in self-defence.

Earlier the same day as the security council resolution, it was reported that

warships from both countries [US and UK] repelled a barrage of 21 Houthi rockets, drones and cruise missiles apparently fired at western warships in the Red Sea

From the second Guardian article linked in the question:

A key provision of Wednesday’s security council resolution, which was sponsored by the US and Japan, noted the right of UN member states, in accordance with international law, “to defend their vessels from attack, including those that undermine navigational rights and freedoms”.

In a statement the UK's Prime Minister Rishi Sunak cited self-defence, saying the UK had

"taken limited, necessary and proportionate action in self-defence, alongside the United States with non-operational support from the Netherlands, Canada and Bahrain."

ICRC Casebook - Self-defence:

It refers to the use of force to repel an attack or imminent threat of attack directed against oneself or others or a legally protected interest.

Self-defense in international law refers to the inherent right of a State to use of force in response to an armed attack. Self-defense is one of the exceptions to the prohibition against use of force under article 2(4) of the UN Charter and customary international law. ...

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In comments, the questioner asked for "references" where "Houthis targeted US and UK ships".

Wikipedia is maintaining a Timeline of the Red Sea Crisis that includes "Attacks on shipping in the Red Sea and Indian Ocean 2023–2024".

Galaxy Leader is owned by Galaxy Maritime Ltd, a company registered in Isle of Man, a British Crown Dependency. This ship was hijacked by Houthi forces on 19 November 2023.

There are two British-owned/managed ships: Unity Explorer and Number 9 (sailing under foreign flags), both attacked on 3 December 2023. Unity Explorer was "Attacked unsuccessfully with an anti-ship ballistic missile, then successfully with another". Number 9 was attacked with a missile.

USS Carney (a US Navy vessel) has been operating in the Red Sea, escorting ships, providing emergency assistance to vessels and intercepting rockets, drones and missiles fired by the Houthis. "On 3 December 2023, Carney and civilian-owned commercial ships were attacked in international waters in the southern Red Sea, with anti-ship ballistic missiles fired from Yemen by Iranian-backed Houthi rebels" (Wikipedia).

USS Mason (a US Navy vessel), assisting Ardmore Encounter (carrying US-owned jet fuel), was "targeted by a UAV" on 13 December 2023 (see timeline article).

On 30 December 2023, Houthi forces attacked Maersk Hangzhou and on 31 December the Houthis attempted to board it. In reaction to the boarding attempt USS Dwight D. Eisenhower and USS Gravely sent helicopters to defend the commercial vessel, which were fired on by the Houthis.

With regard to 9 January 2024, the official position of the UK government is that there was "deliberate targeting of HMS Diamond and US Navy vessels" by the Houthis. So far as I'm aware the US government has not said the US Navy vessels were deliberately targeted, however the US and UK vessels were - along with commercial vessels - in the area that the 21 Houthi rockets, drones and cruise missiles were flying towards.

On 12 January 2024 a tanker that happened to be carrying Russian oil was attacked by Houthi forces. Ambrey, a British maritime security firm, speculated the vessel was mistakenly targeted based on out-dated information that linked the ship to the UK.

On 14 January 2024, the US military said an anti-ship cruise missile had been fired from a Houthi-controlled area of Yemen towards USS Laboon and shot down (Centcom.mil).

On 15 January 2024, M/V Gibraltar Eagle, a US-owned vessel was struck by an anti-ship ballistic missile fired by the Houthis (Centcom).

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Further to the argument about self-defence, see Lawfare's article Attacks on U.S. Warships Justify Self-Defense Against Houthi Forces Ashore, published prior to the US/UK strikes on Houthi forces on 11 January 2024.

Answer 2

Lag's answer is better. I wanted to add direct notes about UN and self defense.

Article 51 of the UN Charter:

Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security.

So nothing in the UN impairs the US or the UKs right to return fire.

There are more relevant agreements that apply more specifically to protect trade, which could separately apply to this context. But once you start getting shot at, the UN explicitly does not bar you from shooting back.

The Houthis have fired a lot of ordinance at both trade vessels and military vessels.

Answer 3

The US and UK can't appeal to article 51 self-defence, not Houthis nor Yemen did not attack the US or UK territories or bases first. The US or UK can't to attack territory of the sovereign Yemen state legal. Only 51 able let attacks of the foreign territory legal. Pirates are the robbers on ships, pirates defence let attack only pirate ships that are in the sea, on the ground.

Ofc, probably, these are outdated rules, while any able to use bombs carrying drones or missile striking. But outdated rules does not let anyone to broke the International Law, and be standing on the right side in same time.

And anyway the ships may always go another way, that is a safe one.

The US and UK are violating International Law while attack Yemen territory. But they are also using logic of rules-based order.

And also i have to say, that Houthis attacks are targeting the US and UK ships that deliver cargos to Israel warring in Gaza. Houthis support Gaza side.

And the resolution is here S/RES/2722(2024), and it is very short to read, only 2 sheets of paper.

The text of resolution does not content any permition to attack the foreign state territory.

Ofc the 3 part may create distored understanding if it is only "...to defend their vessels from attacks, including those that undermine navigational rights and freedoms." But if you read all the third part, it is clear thing that before this phrase war the general term.

3. Affirms the exercise of navigational rights and freedoms by merchant and commercial vessels, in accordance with international law, must be respected, and takes note of the right of Member States, in accordance with international law, to defend their vessels from attacks, including those that undermine navigational rights and freedoms;

The UN Charter does not let to "use force against the territorial integrity or political independence of any state":

2.4. All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.

Also Houthis are not ever pirates.

article 101 Law of the Sea:

Piracy consists of any of the following acts:
(a) any illegal acts of violence or detention, or any act of depredation, committed for private ends by the crew or the passengers of a private ship or a private aircraft, and directed: (i) on the high seas, against another ship or aircraft, or against persons or property on board such ship or aircraft; (ii) against a ship, aircraft, persons or property in a place outside the jurisdiction of any State;

(b) any act of voluntary participation in the operation of a ship or of an aircraft with knowledge of facts making it a pirate ship or aircraft;
(c) any act of inciting or of intentionally facilitating an act described in subparagraph (a) or (b).

Houthis was not the crew or passengers. They had not operate any of ships.

And also very important thing, who thing that Huthis may be pirates or else but the Law of the Sea 1982.

The US did not subscribe United Nations Convention on the Law of the Sea.