Donald Trump holds a chart of military hardware sales as he welcomes Saudi Arabia's Crown Prince Mohammed bin Salman in the Oval Office in May 2018.

As President Donald Trump’s critics focus anew on whether he obstructed justice to thwart Special Counsel Robert Mueller’s investigation, a more flagrant abuse of presidential power is unfolding in plain sight.

For weeks, Trump has continued America’s involvement in the war in Yemen, siding with Saudi Arabia against Congress, the body that the Constitution vests with the power to declare war. The House last month approved a resolution, 247 to 175, directing the president to withdraw the U.S. from the war on Yemen. A bipartisan Senate majority had already approved the same resolution. And the American public has no appetite for a long war in Yemen.

On its own, waging war after an official call from Congress to stop doing so ought to be regarded as a violation of the Constitution that warrants impeachment.

But there’s even more to the Trump administration’s “Saudi Arabia First” foreign policy: Citing a provision in the Arms Export Control Act that allows the president to bypass the legislative approval process in an emergency, the administration is circumventing a block on arms sales to the Saudis.

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“We have the constitutional duty to declare war and the responsibility to oversee arm sales that contravene our national security interests,” Democratic Senator Chris Murphy has complained. “If we don’t stand up to this abuse of authority, we will permanently box ourselves out of deciding who we should sell weapons to.”