The Houthi Attack and the Constitution
A while back it was reported that the U.S. Navy had fired on radar installations of the Houthi rebels in Yemen, after the Houthis fired missiles at U.S. navy ships. The constitutional implications of this affair have (as far as I know) not been much discussed.
Obviously there is no congressional authorization for military action against the Houthis (they have not even a tenuous relationship with al Qaeda or Iraq). So the authority must come from the President's independent constitutional powers. Conventional wisdom no doubt says that since the Houthis attacked U.S. navy ships, the President could direct those ships to respond. I agree, but the issues may not be as simple as they appear.
Some people have a very narrow view of the President's power to respond to attacks, basically derived from Madison's comment at the constitutional convention that vesting Congress with the power to declare war would leave the President with the power to "repel sudden attacks." Thus, it is said, the President has the power to direct the armed forces to react defensively when attacked.
Is that what happened with the Houthis? Maybe. But it seems that the navy first defended itself against incoming missiles and then (after some lapse of time) fired on the radar installations (as the press account says) "retaliating" for the attacks (or perhaps more charitably, to prevent further attacks). If the President's independent power is only to "repel" attacks, perhaps this went further. And if the President has power to "retaliat[e]" for attacks, or to use preemptive force to prevent prospective attacks, then the President's power is a bit more than purely defensive, and one might fairly ask why it does not go quite a bit further than that.
My view is that the President's power does go quite a bit further. But that claim in turn raises this question: is the President now empowered to use the full force of the U.S. military to defeat the Houthis, assuming he would want to do that? I think the answer to that question is "no."
In general, I think that an attack on the United States or U.S. forces gives the President full power to counterattack. Adopting Hamilton's view, that is because the foreign power has declared war on the United States. Once war is declared, the President has constitutional power to fight it. Congress' declare war power is not implicated, because war already exists due to the acts (or statements) of the other side.
In this case, however, it is not clear that the Houthi forces as a whole intended to initiate war with the United States. The press account says:
The Houthis, who are battling the internationally-recognized government of Yemen President Abd Rabbu Mansour al-Hadi, denied any involvement in Sunday's attempt to strike the USS Mason. On Thursday, the Houthis reiterated a denial that they carried out the strikes and said they did not come from areas under their control, a news agency controlled by the group reported a military source as saying.
Thus it appears that the missile attack does not constitute a declaration of war by the Houthis. Perhaps it was a rogue operation, or at least something unauthorized by the Houthi central command (if there is such a thing), or even an attack by some other group. In that case, it would not seem to create the condition of open warfare between the U.S. and the Houthis. The U.S. strikes against the actual forces that carried out the initial attack would still be within the President's power, but widening the conflict to include the Houthi movement as a whole would not be the President's prerogative, without approval of Congress.
One broader point: it is often argued (by presidential advocates) that historical practice shows that the Preisdent has often used military force without Congress' approval. That historical record, presidential advocates continue, shows that the President does not need Congress' approval to use military force. The Houthi incident illustrates the sleight of hand involved in such claims. I would not dispute (and I think few people would dispute) the President's power to order the strikes on the Houthi positions. But that says nothing about a supposed broader power of the President to use military force when he thinks it appropriate. The President's authority to use force against the Houthis in this situation is based on (and limited to) the particular narrow circumstances of this situation. The fact that the President has independent power to use force without congressional authorization in some circumstances does not support the President's power to use force in other situations.(For more on this objection, see here).