For a generation, Democrats stood up against Republican presidents who they deemed to be too eager to go to war—or too ready to put troops in harm’s way without the full consent of the American people through their elected representatives in Congress.

Where have those Democratic protectors of the constitutional authority of Congress gone? Was it always just a partisan attack on Republican presidents?

If not, when will Democrats—who so vociferously opposed a Republican president’s extraconstitutional war-making powers—stand up and oppose President Obama’s unconstitutional usurpation of war-making powers?

Yale Professor Bruce Ackerman puts it succinctly: “The war against the Islamic State is now illegal. The War Powers Resolution of 1973 gave President Obama 60 days to gain consent from Congress and required him to end ‘hostilities’ within 30 days if he failed to do so. This 90-day clock expired this week.” And yet, there’s been no consent, and no end to the fighting.

I believe the president must come to Congress to begin a war. I also believe the War Powers Act is misunderstood; President Obama acted without true constitutional authority even before the 90 days expired, since we were not under attack at that time.

But in either case, this war is now illegal. It must be declared and made valid, or it must be ended.

Congress has a duty to act, one way or the other.

But it’s not the only area where action is needed. This is, of course, not the only way in which this president is acting like a king.

Conservatives have rightly decried President Obama’s unconstitutional executive action on Obamacare—and his promises to do the same with immigration. With both branches of Congress now under Republican control, we should act to halt those power grabs, too.

But conservatives can’t simply be angry at the president’s lawlessness when they disagree with his policies. They should end their conspicuous silence about the president’s usurpation of Congress’ sole authority to declare war—even if (especially if) they support going after ISIS, as I do.

This is important. We can’t be for the rule of law at our own convenience. It matters how we act both when we agree and when we disagree with the president.

Conservatives who blast the president for ignoring the separation of powers on immigration display a fatal inconsistency by embracing unlimited war-making powers.

Secretary of State Kerry became famous as an anti-war liberal decades ago, when he asked Congress “who will be the last to die for a mistake.”

That same man is now probably the most visible liberal proponent of unlimited war-making powers, as a member of this administration.

When I asked him at a Senate Foreign Relations Committee hearing how on God’s green Earth a resolution to use force against the perpetrators of 9/11 in Afghanistan could be construed to apply to the Islamic State in Iraq in 2014, he replied that it didn’t matter. The president could justify basically any war making as an “Article II” power.

For those who believe in unlimited Article II power, the argument goes that since Article II makes the president the “commander in chief” and that really Congress is only a flimsy appendage to be grudgingly consulted—but never to be bound by.

Recent attempts to replace the War Powers Act miss the point completely and attempt to mandate more consulting but do nothing to reinforce or acknowledge the primary point: that the Constitution demands authorization for a war—not a cup of tea while the war drums beat.

This argument is vital to a larger argument: Do we obey the rules set up to constrain government or not? Do we survive as a constitutional republic, or not?

Prominent Republicans from the interventionist wing of the party parrot and applaud Kerry’s position. If ever there was too much bipartisanship, it would be the bipartisan acceptance of unlimited presidential war-making power.

Conservatives should realize, though, what unfettered presidential power means. Proponents of this theory argue that congressional laws cannot limit the president’s power to perform warrantless searches, carry out wiretaps, detain perceived enemies of the state, or even torture people—not just of enemy soldiers, but American citizens not engaged in combat.

Apologists for unlimited presidential war power, like former Bush administration official John Yoo, claim that no law “can place any limits on the president’s determinations as to any terrorist threat, the amount of military force to be used in response, or the method, timing, and nature of the response.” Yoo further argues for unchecked executive power by claiming that the explicit constitutional power for Congress to declare war is really not a check at all. In a remarkable work of double-speak, Yoo writes that the Declare War Clause does not grant Congress any power to initiate war, but only the “judicial power” to recognize whether “the nation was [already] in a legal state of war” for purposes of “domestic” law.

It would appear that these advocates of unlimited Article II powers would even argue that fundamental Bill of Rights privileges could be ignored in time of war. For those who argue but this will only occur in the dangerous time of war, realize that we are now engaged in war that has no temporal or geographic limits. Realize that we now have soldiers fighting a war that began when they were toddlers and shows no signs of ending.

Unchecked government power, without the necessary checks and balances, is contrary to our heritage and allows for injustices most Americans would find appalling, such as indefinite detention without legal representation and torture of American citizens.

Fred Korematsu was one of the thousands of Japanese Americans interned during WWII by people who believed in unlimited presidential power. Korematsu knew firsthand the dangers of war-time hysteria and pleaded that we not make that mistake again.

Not only is the Constitution explicit that war is to be initiated by Congress alone, our Founders doubled down on this proposition in the Federalist Papers. Madison wrote that history demonstrates what the Constitution supposes, that the Executive Branch is the branch most prone to war, therefore the Constitution vested the power to declare war in the legislature.

If the Constitution were not enough, the War Powers Act reiterates the legislature’s prerogative. The War Powers Act does not allow for any military action to take place that is not authorized by Congress or to repel imminent attack. Period. The only exception is military action to repel an imminent attack. In that case, the president has 60 days to report to Congress. Obviously, it’s an exception that doesn’t apply to any of our current wars.

This administration has allowed, as Professor Michael J. Glennon writes, “nothing less than a collapse of the equilibrium of power, the balance expected to result from ambition set against ambition, the resistance to encroachment that was supposed to keep the three branches of the federal government in a state of equilibrium and to protect the people from the government.”

It’s time for conservatives to say enough is enough. Obama’s commandeering of Congress’s powers—from making war, to remaking our health-care system—has to stop. There needs to be an across-the-board, consistent defense of the constitutional separation of powers. Nothing less will win the day. That should include this current battle in the Middle East. Taking military action against ISIS is justified. The president acting without Congress is not.