Last week, the Obama Justice Department’s Office of Legal Counsel released its formal opinion [.pdf] on the President’s “Authority to Use Force in Libya.” OLC is the professional corps providing advice to the president on the legality of his actions, and it’s a much-coveted berth for ambitious lawyers. But, reading the memo over (it’s officially dated April Fool’s Day—make of that what you will), it occurred to me that, personally, I’d sleep better at night as in-house counsel for Fannie Mae or Archer Daniels Midland.

Though the Office is supposed to help the president “take Care that the laws be faithfully executed,” OLC lawyers typically end up telling their immediate employer, “why, yes: the action you’ve already decided to take turns out to be perfectly constitutional.” The Libya memo perfectly illustrates that dynamic.

Per OLC, the constitutionality of our Libyan adventure “turns on two legal questions”:

1. Do the bombing raids and airstrikes the president ordered “serve sufficiently important national interests” to make them permissible exercises of his constitutional powers as “Commander in Chief and Chief Executive”?

2. are “the military operations that the President anticipated ordering” limited enough in “nature, scope, and duration,” such that they do not “constitute a ‘war’ requiring prior specific congressional approval under the Declaration of War Clause?”

In a post over at the Washington Examiner’s blog, I address the second argument, pointing out that, by the Secretary of Defense’s own admission, what we’re doing in Libya is “war,” even if the Obama team prefers Orwellian euphemisms like “kinetic military action.”

As for the first question, whether airstrikes on Libya serve “sufficiently important national interests,” is quite beside the point. The Constitution either gives the president the power to start nondefensive wars or it doesn’t. (It doesn’t). Whether any particular use of the asserted power is “in the national interest” isn’t a legal question, and executive branch lawyers in the president’s thrall are about the last people anyone actually interested in the national interest would consult for the answer.

There are many more problems with OLC’s constitutional case for war than I can treat in a single blogpost, but I’ll address one of them here (with more to come later, time permitting).

The OLC memo makes much of the “historical gloss” that they imagine coats the Constitution on account of past practice. The president’s lawyers note that prior presidents have used force abroad repeatedly without congressional approval, and assert that:

This historical practice is an important indication of constitutional meaning, because it reflects the two political branches’ practical understanding, developed since the founding of the Republic, of their respective roles and responsibilities with respect to national defense.

This is a familiar argument, but it’s bad history and bad constitutional theory.

The notion that past practice justifies current abuses has been a familiar one since Harry Truman’s “police action” in Korea, when one Democratic Senator justified Truman’s move by arguing that “on more than 100 occasions,” the president had ordered US forces into action without seeking congressional approval.

But as constitutional scholar Edward S. Corwin noted at the time, the majority of those episodes consisted of ‘‘fights with pirates, landings of small naval contingents on barbarous or semi-barbarous coasts, the dispatch of small bodies of troops to chase bandits or cattle rustlers across the Mexican border, and the like”–many of which were undertaken to protect American citizens, and most of which (before the 20th century at least) were consistent with the president’s constitutional power to “repel sudden attacks.”

Besides, if what you’re trying to do is figure out the original public meaning of constitutional text, the practice that counts most is early practice, contemporaneous with the people that ratified the text and had to interpret it. And there the record’s pretty clear. In his four-book series The Constitution in Congress, the University of Chicago’s David Currie exhaustively examined congressional and presidential interpretations of the Constitution in the young Republic. With regard to the Constitution’s allocation of war powers, Currie concluded that:

despite the usual line-drawing and factual difficulties the express position of every President to address the subject during the first forty years of the present Constitution was entirely in line with that proclaimed by Congress in the celebrated War Powers Resolution in 1973: The President may introduce troops into hostilities only pursuant to a congressional declaration of war or other legislative authorization, or in response to an attack on the United States.

But even had that not been the case, what would past practice add to the argument for presidential power? Anyone who sets up a written Constitution recognizes the possibility that the political branches might violate the original agreement. If those violations instead become, as OLC suggests they should, evidence of the “two political branches’ practical understanding”–indicative of constitutional meaning itself–then we have problems that go beyond our current difficulties with constitutional war powers. If misbehavior by the political branches alters the meaning of the constitutional text, then the administrative state is perfectly constitutional, bridges to nowhere are A‑OK under the General Welfare clause, and mandating low-flow toilets is an acceptable exercise of Congress’s regulatory power under our miraculously “glossy” Constitution.

When two branches gang up on the people and get away with it, OLC calls that “precedent.” But we have good reason to be wary of the argument that violations of the Constitution somehow amend the Constitution. It’s an argument that repudiates constitutionalism itself.