In a recent post at the Originalism Blog, prominent originalist legal scholar Michael Ramsey notes the phenomenon of nonoriginalists like Sen. Bernie Sanders claiming that Trump's recent air strike on Syria requires congressional authorization. In Ramsey's view, this conclusion is difficult to justify on other than originalist grounds:
I agree [with Sanders].... But let's be clear that Senator Sanders and those agreeing with him are making an originalist argument. The Constitution given its original meaning is clear.... To "declare war" in eighteenth-century terms included "declaring" by taking military action as well as by issuing a proclamation, and even relatively small armed conflicts with foreign nations were considered "war."
In contrast, the nonoriginalist case against the President's war-initiation power is highly uncertain. It can be made....
But the argument the other way is strong as well. Circumstances have changed drastically since the Founding. Military action can take place much more quickly, and often needs to do so to be effective. The United States' air power superiority makes quick strikes more practical and less likely to involve material U.S. casualties. The power disparity and our limited objectives make it less likely that full-scale war will ensue. Congress has proved unwilling to wield the war-initiation power except for major conflicts (and sometimes not even then). Presidents have used their independent power to launch airstrikes repeatedly in modern times -- Clinton in Kosovo, Obama in Libya, Trump in Syria last year -- with relatively muted criticism. The President's lawyers have consistently taken the position across multiple administrations that Presidents have this power. No Supreme Court decision in modern times has even hinted at a limitation, as the Court has carefully avoided the issue.
Taking all these arguments together, there's a strong claim that the Constitution's meaning has evolved, or should be seen as evolving.
I think the nonoroginalist case for requiring congressional authorization is stronger than Ramsey gives it credit for. As Ramsey notes, the main living Constitution justification for letting the president initiate wars on his own is the greater need for speed in an era when events move more quickly than in the 18th century. But this ignores the reality that modern technology also makes it possible to get swift congressional authorization. In the 1790s, it could take weeks to gather all of the members of Congress in Washington when the legislature was out of session. Today, by contrast, modern jet travel enables virtually all of them to get back to DC within less than a day. No significant US military intervention has ever been decided on so quickly that Congress could not have been summoned to Washington in time, even if out of session. In this context, it is important to remember that we are talking about the power to initiate conflicts with foreign powers that the US was previously at peace with. No one denies that the president has the authority to respond if the other side attacks first (and thereby itself initiates war).
When we begin the conflict ourselves, there is little to lose by taking a few days to get congressional authorization. Perhaps we would lose the advantage of surprise. But virtually every presidentially initiated conflict of the last several decades came only after considerable public debate and rumors of imminent military action. None were "bolt from the blue" attacks that took the enemy completely by surprise.
It is true that some modern military actions have "limited objectives" and are likely to involve few or no US casualties. But, of course, the same was true of many 18th and 19th century conflicts. That is not much of a material change. By contrast, the existence of nuclear weapons and other weapons of mass destruction in modern times creates a risk of massive escalation, in some cases, that did not exist in earlier eras. That argues for greater caution and deliberation before launching attacks.
The claim that presidential unilateralism is validated by practice has some truth to it, but is a lot weaker than it seems. The vast majority of the cases usually cited were in fact either interventions small enough that they did not rise to the level of war, or cases where the enemy attacked first, thereby initiating the war themselves. There are some important exceptions, such as the Korean War, Kosovo, and Obama's Libya intervention. But the existence of exceptions does not obviate the rule. Few if any constitutional constraints on government power are perfectly enforced. Constitutional rules are not like virginity. Violating them once or even multiple times does not mean they must be lost for ever.
Some of the Founding Fathers' reasons for giving the power to initiate war to Congress are actually more compelling today than in their own time. Their greatest concern was ensuring that no one person would have the power to take the nation to war. As James Madison put it, "the trust and the temptation would be too great for any one man." This is an even more serious danger in an era when the Oval Office can be occupied by a dangerously impulsive and ignorant demagogue, thanks in part to the breakdown of political safeguards against such an eventuality. The Founders expected that such dangerous men would be kept away from the presidency by institutions such as the electoral college, which was supposed to exercise independent judgment and screen out demagogues. But, as early as the first contested elections in 1796 and 1800, it became clear that most electors would simply vote the party line. In later periods, party elites exercised a similar screening function by controlling the nomination process. That has obviously broken down in recent years, as the process has become more populist, leading to the election of Trump.The Founders' fear that a president might launch a war to distract attention away from domestic political problems is also more plausible under modern conditions, where vivd 24 hour cable TV news coverage enables even a distant war to dominate public attention to a greater degree than was feasible two centuries ago.
In sum, both originalists and living constitutionalists have good reason to conclude that the Constitution bars the president from initiating war without congressional authorization. There is, of course, some room for debate about which military actions are large enough to be considered wars. But sustained engagements that involve combat over a period of weeks, months, or longer, surely qualify.