Last Friday, as part of a broader attack on President Obama's "imperial" tendencies, Sen. Ted Cruz (R-Texas) criticized the Justice Department for indicating that it will not prosecute marijuana growers and sellers who comply with state law, provided they are properly regulated. Speaking at a Texas Public Policy Foundation conference in Austin, Cruz said this prosecutorial forbearance illustrates Obama's habit of ignoring the law when obeying it would prevent him from doing what he wants:

A whole lot of folks now are talking about legalizing pot….And you can make arguments on that issue. You can make reasonable arguments on that issue. The president earlier this past year announced the Department of Justice is going to stop prosecuting certain drug crimes. Didn't change the law. You can go to Congress. You can get a conversation. You could get Democrats and Republicans who would say, "We ought to change our drug policy in some way," and you could have a real conversation. You could have hearings. You could look at the problem. You could discuss commonsense changes that maybe should happen or shouldn't happen. This president didn't do that. He just said, "The laws say one thing"—and mind you, these are criminal laws; these are laws that say if you do X, Y, and Z, you will go to prison. The president announced, "No, you won't."

Contrary to the Raw Story headline, Cruz said nothing about "locking up marijuana users in Colorado." The federal government generally avoids penny-ante pot cases, and it has never made busting cannabis consumers a priority. Almost all such arrests are made by local police. But that very fact suggests something is wrong with Cruz's argument. Since possessing any amount of marijuana is prohibited by the Controlled Substances Act, did Obama's predecessors forsake their duty to uphold the law by focusing on big pot cases? Or were they exercising appropriate discretion in deciding how best to allocate federal law enforcement resources?

That is precisely what the Justice Department claims to be doing in connection with states that have legalized marijuana for medical or general use. In his August 29 memo outlining the policy, Deputy Attorney General James Cole said it is all about "using [the department's] limited investigative and prosecutorial resources to address the most significant threats in the most effective, consistent, and rational way." With that goal in mind, Cole said, U.S. attorneys should focus on cases that implicate "certain enforcement priorities," including preventing marijuana consumption by minors, diversion to to the interstate market, and drugged driving or "the exacerbation of other adverse public health consequences associated with marijuana use."

Contrary to Cruz's implication, the memo offers no guarantees. Federal prosecutors can decide to crack down on state-legal marijuana producers and retailers at any time for one of the reasons Cole mentions or for other reasons they make up on the fly. The memo closes with a warning that "nothing herein precludes investigation or prosecution, even in the absence of any one of the factors listed above, in particular circumstances where investigation and prosecution otherwise serves an important federal interest."

Cruz therefore is wrong to suggest that the administration has declared the Controlled Substances Act inoperative in states that have legalized marijuana. Nor does the policy described in the Cole memo violate that statute, which has never been enforced against every violator. In that respect Obama's grudging tolerance of marijuana legalization differs from, say, his decision to ignore certain provisions of the health care law he championed when they became inconvenient—another, more apposite example of lawless presidential action cited by Cruz.

Speaking of Obamacare, it is rather strange to see one of its leading opponents argue that the president should seek to scuttle marijuana legalization in Colorado and Washington. The main constitutional problem with the Patient Protection and Affordable Care Act is that it exceeds the federal government's authority under the Commerce Clause (an issue the Supreme Court dodged by implausibly treating the penalty for failing to obtain government-approved medical coverage as a tax). The same is true of the federal ban on marijuana, at least insofar as it purports to criminalize intrastate activity. In fact, the 2005 Supreme Court decision upholding enforcement of federal marijuana prohibition against patients in states that allow medical use is widely seen as the most extreme example of stretching the Commerce Clause beyond recognition to accommodate every congressional whim. "If Congress can regulate this under the Commerce Clause," Justice Clarence Thomas observed in that case, "then it can regulate virtually anything—and the Federal Government is no longer one of limited and enumerated powers." Yet here is Cruz, an avowed constitutionalist and federalist, demanding that Obama impose marijuana prohibition on states that have opted out of it, based on an absurdly broad reading of the power to regulate interstate commerce.