The President’s request for congressional authorization to use the armed forces against ISIS is another page in the long and occasionally contradictory history of executive-legislative relations when it comes to the question of who has authority in situations like the one the country faces today. According to the Constitution, the President is the Commander-in-Chief of the armed forces, but only the Congress may declare war. There are times when the President does not need to seek authorization to use armed forces. For example, it is generally accepted that the President can use force to repel an invasion. Commanders-in-Chief usually take an expansive view of what constitutes such a situation allowing them to deploy forces without congressional approval. So there is a natural constitutional tension, which occasionally surfaces. In 1973, Congress tried to rein in the President by passing the War Powers Resolution, which allows Congress to pass a disapproval resolution 60 days after the President deploys troops into combat without the legislature’s prior authorization. President Richard Nixon vetoed the legislation, but it was on of the relatively few times that a veto has been overridden. Down the decades, the Presidents have disputed the constitutionality of the War Powers Resolution. For instance, when President George W. Bush signed the authorization for use of force in Iraq, he noted:

While I appreciate receiving that support, my request for it did not, and my signing this resolution does not, constitute any change in the long-standing positions of the executive branch on either the President’s constitutional authority to use force to deter, prevent, or respond to aggression or other threats to U.S. interests or on the constitutionality of the War Powers Resolution.

In 2013, when the Administration sought congressional support to punish Syrian President Bashar al-Assad for using chemical weapons against his own people, the legislature dealt the President Obama a humiliating defeat by refusing to approve military action. However, last summer when Members of Congress were calling for authorization for use of force against ISIS, the President maintained that he already possessed the legal authority to attack, but would appreciate congressional authority.

Despite the tensions that flare up—and even Congress’ refusal to assent to the use of force against Syria—Congress is traditionally loath to tie the President’s hands when it comes to military action. As the old saying goes, politics stops at the water’s edge. We discussed this phenomenon in September 2013, in the midst of the discussion over whether the United States would attack Syria:

When President Reagan launched a retaliatory military strike against Libya for its complicity in a terrorist attack in Berlin, there was no request for congressional approval.  When Reagan launched an invasion of Grenada to secure the release of American medical students, Congress largely applauded the action.  When President Clinton launched air strikes in Kosovo against the Serbian army, he did not seek congressional authorization. Most recently, when President Obama used the military (including special forces), the CIA and other American personnel in Libya, he did not ask Congress for authorization.  The Libya operation continued for more than 60 days, and Congress was within its legal rights to pass a motion of disapproval – but politically, the Democrats in Congress did not want to undermine President Obama, and the Republicans in Congress were not sure they wanted to tie the hands of future Presidents to use military force. Without addressing the question of whether any of these actions had legal warrant, each of them reinforces the notion that the President may use the military without congressional authorization, and that Congress has largely conceded the point.

Recognizing the threat that ISIS poses and the turpitude of its crimes, Congress will likely pass kind of authorization in this case, but neither the President nor his successors will likely view it as a concession the legislature on the general principle of when the Commander-in-Chief may use military force.

Aside from legislative-executive tensions, the anti-ISIS AUMF also shows the limits of how far political parties can keep together. In drafting this AUMF, the White House must satisfy several different groups. First, and most importantly, is the American people, who support a response to ISIS. (The Brookings Institution released a report in early January concluding that 57 percent of the public “believe that the United States must do whatever is necessary in order to defeat ISIS”.) Secondly, he must work with the Republicans who control Congress. This won’t be easy. Speaker of the House John Boehner expressed reservations about the AUMF, releasing a statement saying, “we need a comprehensive military strategy and a robust authorization, not one that limits our options”.

Unless the President is willing to ignore his own party and work solely with the Republicans, he’ll have to balance the Democrats’ concerns as well—which could prove tricky too. After White House officials briefed Democrats on the proposed AUMF, a number, some quite influential, expressed reservations and criticisms. For instance, Senator Barabara Mikulski of Maryland told National Journal that despite her “support [for] the general framework”, she has “significant questions”, particularly about the role ground forces might play in the process. “I don’t know what the word ‘enduring’ means. I’m very apprehensive about a vague, foggy word, and enduring is not in the eyes of the beholder.” Politico reported that Senator Richard Blumenthal of Connecticut said, “I have yet to be convinced. We’re all consulting at this point with each other, generally struggling for a consensus.”

To come to some kind of “consensus” with the Democrats and Congress in particular, the President will have to satisfy his own party members who tend to be more wary of long-term military engagements and the Republicans who desire a more “robust” one. That is a tricky 7-10 split. Normally, it would be unlikely that parties would be able to come to an accord on a difference that big. The example of the failed Syrian authorization shows that the President doesn’t always get what he wants. However, since ISIS’ atrocities include the butchering of American civilians, Members of Congress will be more inclined to support the President. But how much of a consensus will the final AUMF debated by Congress inspire? Inevitably, quite a few Members—particularly Democrats—will be dissatisfied with the finished product, but will they nonetheless vote for it as a show of unity? Or if the Republican leadership brought up an AUMF wholly to their liking, would the Democrats reject it, even if the President agreed to sign it? Those will be the questions to watch over the next few weeks.