David Rivkin served in the Justice Department during the Reagan and George H.W. Bush administrations. He represented the 26 states in their challenge to the 2010 Affordable Care Act before the trial and appellate courts. Joe Jacquot is a former deputy attorney general of Florida and a former chief counsel of the Senate Judiciary Committee’s subcommittee on immigration.

The Obama administration has taken federal-state relations to a new low in its quest for an unprecedented expansion of presidential power. In response to Arizona’s efforts to identify and arrest undocumented immigrants, the president claims that he can preempt state law whenever its enforcement might irritate a foreign government. This unconstitutional power grab cannot stand.

While the challenge by 26 states to the 2010 Affordable Care Act seeks limits on Congress’s powers, the Arizona law defends the fundamental authority of states to act in contravention of the president’s preferences. There is genuine controversy over the Arizona immigration policy of penalizing illegal immigrants , designed to drive down their numbers and reduce the burdens on the state budgets and institutions, but the case the Supreme Court recently agreed to hear poses broader legal questions that go to our Constitution’s most fundamental principles, executive power and state sovereignty.

Under the Constitution, some powers are exclusive to the federal government or the states, while others are shared. By limiting the federal government’s reach to authorities found in specific, enumerated grants of power, the Constitution reserves broad authority for individual states. States retain traditional “police power” to legislate on issues of public safety and welfare.

Arizona relied on its police power in passing the immigration-related law the Obama administration has challenged. That law’s most controversial provisions make Arizona state and local law enforcement responsible for investigating possible violations of federal immigration law. If an officer has reasonable suspicion that a person encountered during a police stop or detention is in this country illegally, the officer must check the person’s immigration status. If immigration authorities confirm that the person is illegal, the officer must arrest him or her.

No one disagrees that Congress could preempt state efforts to enforce immigration law, under its constitutional power to “establish a uniform rule of naturalization.” But Congress actually rejected that approach. Instead in the 1996 statute, it afforded the states broad flexibility to address immigration-related matters consistent with federal statutory requirements. The Supreme Court held as much last year when it approved another Arizona law that revokes the permits of businesses that hire illegal workers.

Nevertheless, the Obama administration claims that federal power preempts Arizona’s law in two ways. First, it has argued, in court filings intended to strike down the Arizona law under the Constitution’s “supremacy clause,” that federal law prevails when state law conflicts with it. The administration argues that, as Congress has authorized the executive branch to identify and detain illegal immigrants, the president’s decision not to enforce the law creates a conflict.

But no precedent suggests that the president’s refusal to carry out Congress’s wishes, as expressed in law, somehow prevents a state from doing so or renders its actions contrary to congressional intent, which is the appropriate standard for preemption. And that argument is especially ludicrous in this instance, where Congress specifically required federal officials to inform state and local law enforcement of a person’s immigration status when requested. In this way, federal law actually supports and facilitates Arizona’s enforcement approach. Congress’s intentions could hardly be clearer.

The administration’s fallback argument is simply that the president has unilateral power under the Constitution to nullify Arizona’s law respecting immigration. Mexico, the administration explains, has lodged complaints regarding Arizona’s law, and this implicates the president’s power over foreign affairs, which in turn trumps Arizona’s immigration-related actions.

This is a stunning and audacious power grab, far more expansive than the legal theories that prompted critics of President George W. Bush to argue that he established an “imperial presidency.” It simply cannot be that, despite all the Constitution’s limitations on federal power and executive action, the president’s powers become absolute whenever another nation complains.

Indeed, the Supreme Court recently rejected even a more limited version of that argument advanced by the Bush administration. In Medellin v. Texas , the court rejected Bush’s attempt to enforce U.S. treaty obligations by blocking Texas’s execution of a Mexican national who had not been given his consular-notification rights. Yes, the court explained, the president is well-placed to resolve sensitive foreign policy decisions, but that status does not confer “unilateral authority to create domestic law” or override state law.

Nearly 60 years ago, in the Youngstown case that famously reversed President Harry S. Truman’s efforts to seize the nation’s steel mills during the Korean War, Justice Robert Jackson explained that “when the President takes measures incompatible with the expressed or implied will of Congress, his power is at its lowest ebb.” When those measures are also incompatible with the basic precepts of federalism, his power is nonexistent. The fact that the Supreme Court granted swift review of this case suggests that it will repudiate the Obama administration’s imperial power grab.