The rule of law is the moral underpinning of U.S. foreign policy. President Barack Obama must now reaffirm that principle.

This task became all the more urgent with the disclosure last week of a secret document that provides the Justice Department’s legal analysis of the targeted killings of suspected terrorists. After NBC News obtained the memo, members of Congress complained that they had been kept in the dark, and the president agreed to share his reasoning.

He needn’t discuss the details tonight. The drone strikes, after all, are classified, as are the details of what constitutes an “imminent threat” warranting a kill order.

However, Obama must send a message to the world by standing up for constitutional accountability in making life-or-death decisions in the gray zone between peacetime and war. The specifics — for example, a court such as the one authorized for electronic surveillance by the 2008 Intelligence Authorization Act or a template for consultation with Congress — are less important right now than making clear the need for explicit rules.

Whatever legal rationales Obama offers will be tested in international bodies, and they will probably be found wanting. Although foreign governments are relieved that the U.S. handles the dirty work of killing terrorists, they are also quick to criticize its failure to win United Nations approval for every international action it takes.

But legal standards that don’t pass global muster are better than no public standards at all, which has been the approach since drone strikes and other targeted killings began.

The lack of such rules increases the risk of retaliation (often many years later) by nations and groups for the perceived sins of the U.S. Lawlessness breeds lawlessness.

Nothing the president says in a speech can prevent the brother or son of a terrorist or of an innocent victim of collateral damage from seeking vengeance in the future.

Even so, by placing his anti-terrorism policy firmly in a legal framework, Obama can offer support to those fighting abusive, unaccountable regimes and reassure his own citizens that he is in full compliance with the U.S. Constitution.

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Jonathan Alter, a contributing editor of the Washington Monthly, is a former senior editor and columnist at Newsweek, a filmmaker, journalist, political analyst, and the publisher of the Substack Old Goats with Jonathan Alter. His most recent book is His Very Best: Jimmy Carter, a Life.