President Obama is soon expected to take a step toward fixing our broken immigration system by issuing an executive order to halt deportations of undocumented immigrants whose children are U.S. citizens. Republicans, including Speaker of the House John Boehner and new Senate Majority Leader Mitch McConnell, have threatened reprisals against such an order. But one thing is clear: The president has the constitutional authority to decide to not proceed with deportations. It has always been within the president’s discretion to decide whether to have the Department of Justice enforce a particular law. As the Supreme Court declared in United States v. Nixon, “the Executive Branch has exclusive authority and absolute discretion to decide whether to prosecute a case.”

A president may choose to not enforce particular laws when deciding how to allocate scarce resources or based on his view of the best public policy. Few object, for example, when the Department of Justice does not prosecute those who possess small amounts of marijuana, even though they violated the federal Controlled Substance Act. There are countless federal laws that go unenforced. In 1800, then congressman and later Chief Justice John Marshall stated, the president may “direct that the criminal be prosecuted no further” because it is “the exercise of an indubitable and constitutional power.”

The president’s broad prosecutorial discretion has been repeatedly recognized by the courts. In 2013, Judge Brett Kavanaugh of the D.C. Circuit, appointed by George W. Bush, offered a strong defense: “The president may decline to prosecute certain violators of federal law just as the president may pardon certain violators of federal law,” Judge Kavanaugh wrote. “The president may decline to prosecute or may pardon because of the president’s own constitutional concerns about a law or because of policy objections to the law, among other reasons.”

This prosecutorial discretion is even greater in immigration because the treatment of foreign citizens is inextricably intertwined with the nation’s foreign affairs, an area especially under the president’s control. For example, the Supreme Court’s decision in 2010 to overturn large parts of Arizona’s restrictive immigration law, SB1070, was premised on the executive branch’s need for discretion in the immigration context. “A principal feature of the removal system is the broad discretion exercised by immigration officials,” the Court wrote, adding that “[t]he dynamic nature of relations with other countries requires the Exec­utive Branch to ensure that enforcement policies are con­sistent with this Nation’s foreign policy with respect to these and other realities.” In a similar 1941 case, Hines v. Davidowitz, the Supreme Court voided a Pennsylvania system of alien registration because “experience has shown that international controversies of the gravest moment, sometimes even leading to war, may arise from real or imagined wrongs to another’s subjects inflicted, or permitted, by a government.”

Indeed, presidents of both parties have tailored immigration policy to their own goals. In 1987, the Reagan administration took executive action to limit deportations for 200,000 Nicaraguan exiles, even those who had been turned down for asylum. Similarly, President George H.W. Bush in 1990 limited deportations of Chinese students and in 1991 kept hundreds of Kuwait citizens from being deported. President Bill Clinton regularly used his power of prosecutorial discretion to limit deportations; in 1993 he gave 18-month extensions to Salvadoran residents, in 1997 he limited deportations for Haitians, and in 1998 he limited deportations to Central American counties that had been devastated by hurricanes.