In a Rose Garden speech Friday, President Obama announced that per a "Homeland Security Directive," his administration had called a halt to deportation proceedings for certain unauthorized immigrants who came to the U.S. as minors. The eligibility criteria stated in the order roughly tracks the requirements of the Dream Act, which has never quite been able to make it through Congress. A mere technicality, the president suggested: it's "the right thing to do for the American people."

In an interview with a panel of Latino journalists last fall, the president had a different take: "This notion that somehow I can just change the laws unilaterally is just not true. We live in a democracy," he insisted. "You have to pass bills through the legislature and then I can sign it." That's why, despite the urging of immigration activists, he could not implement the Dream Act via executive diktat.

But that explanation is no longer operative, to borrow the old Clinton administration euphemism for "I lied." Obama's latest move underscores just how easy it is for modern presidents to "change the laws unilaterally."

As it happens, Obama's "royal dispensation" for young immigrants is hardly the most terrifying instance of administration unilateralism. In fact, as a policy matter, it's a humane and judicious use of prosecutorial resources.

But given the context, it stinks. It looks uncomfortably like implementing parts of a bill that didn't pass, and—carried out as it was with great fanfare and an eye to the impending election—the move sits uneasily with the president's constitutional responsibility to "take Care that the Laws be faithfully executed."

The University of Chicago's Richard Epstein warns that "government by waiver" is "among the most serious challenges to the rule of law in our time." The growth of the administrative state has concentrated enormous discretionary power in the president's hands, and he can use that power to reward political allies and legislate by decree without the inconvenience of democratic deliberation.

Consider the conditional waivers the administration has granted to 10 states, freeing them from the strictures of the No Child Left Behind Act—but only if they adopt certain reforms, nowhere to be found in the law.

As The Examiner's Michael Barone noted last year, the president's union allies were suspiciously overrepresented in Obamacare waivers granted by Health and Human Services Secretary Kathleen Sebelius, loosening administrative cost limits in employer health plans.

"What about employers who do not have the resources to navigate the waiver process?" Epstein asks. "What about those lacking the political connections to make their concerns heard in Washington?"

Many of the major provisions of Obamacare are slated to come on line in 2014, Epstein notes: "Written with only the vaguest legislative language, it will be up to HHS bureaucrats to interpret these mandates and turn them into regulations. Inevitably, those rules will come with some waiver authority—and with it great potential for the differential application of generally applicable laws. The danger posed to the basic principles of the rule of law, therefore, is immense."

Looking abroad, the dangers to the rule of law are equally grave. In an interview with CBS's Bob Schieffer on Sunday, Gov. Romney announced that, when it comes to preventive strikes on Iran, the Constitution's "Declare War" clause is optional.

"I don't believe at this stage, therefore, if I'm president that we need to have a war powers approval or special authorization for military force," he said, "The president has that capacity now."

That's Obama's position on war powers as well—as his Libyan adventure proved. Unfortunately, executive unilateralism is a bipartisan vice.

Gene Healy is a vice president at the Cato Institute, the author of "The Cult of the Presidency," and a columnist at the Washington Examiner, where this article originally appeared.