Events on both sides of the Atlantic yesterday made for an interesting contrast in the way Western democracies go to war. In the United Kingdom, they decided to actually have a vote before letting the bombs fly—with PM David Cameron winning approval in the House of Commons by a wider-than-expected 174-vote margin.

Meanwhile, the Washington Post reports that the Obama administration is sending a new Special Operations task force of some 200 soldiers to Iraq, to “enable the U.S. military to launch additional commando-style operations and increase intelligence collection, both in Iraq and in neighboring Syria.” Thus, while our cousins across the pond have secured legislative approval for war against ISIS, the “world’s oldest constitutional democracy” slips further toward a ground combat role in a war that the president ordered up some 16 months ago without a shred of legal authority. 

American’s fundamental law vests the decision to go to war in Congress. Under British law, however, the decision to use military force is a “prerogative power”—a decision taken by the Prime Minister “on behalf of the Crown.” “In constitutional terms Parliament has no legally established role and the Government is under no legal obligation with respect to its conduct.” And yet, in practice, as F.H. Buckley points out in The Once and Future King: The Rise of Crown Government in America, the British system has lately done a better job than the American one at forcing public deliberation over war: “the government’s day-to-day accountability before the House of Commons make[s] it far more difficult for a prime minister to disregard Parliament’s wishes.” Indeed, the last time Cameron contemplated airstrikes on Syria—over the use of chemical weapons in 2013—he had to abandon the idea after losing the vote in the House of Commons: “Parliament has spoken,” as Foreign Secretary William Hague summed up.

The U.S. Congress hasn’t spoken, in any formal sense, on our latest war in the Middle East, and it’s in no particular hurry to do so. The Obama administration continues to insist that, under the use-of-force resolution Congress passed over 14 years ago, it has all the legal authority it needs to wage war against ISIS, a group that’s also at war with Al Qaeda, the target of the original resolution. That pretext, offered mainly in unsigned “talking points” by anonymous administration officials, is too thin to hide the sweeping claim of executive war power on which the president’s war rests. Oddly enough, today royal prerogative thrives in the country that fought a revolution to overthrow it.