"[Immigration enforcement] has prosecutorial discretion and exercises it every day." That was not President Obama defending his administration's decision last week to defer deportation for several hundred thousand young undocumented immigrants -- it was Immigration and Naturalization Service (INS) Commissioner Doris Meissner discussing her agency's authority back in the year 2000. This might surprise people who believe that the president invented the authority to issue such deportation deferrals. It turns out the policy is not only legal, but was in regular use before the administration's decision to expand it. Meissner specifically noted that this discretion "applies not only to the decision to issue, serve, or file a Notice to Appear (NTA), but also... deciding whom to stop, question, and arrest... settling or dismissing a proceeding, granting deferred action, or staying a final order." The criteria for its use included length of residence, criminal history, humanitarian concerns, military service, availability of resources, and even "community attention." The Supreme Court agrees with this broad reading of discretion. In Heckler v. Chaney, 470 U.S. 821 (1985), the Justices emphasized that "an agency's decision not to prosecute or enforce, whether through civil or criminal process, is a decision generally committed to an agency's absolute discretion." If Rep. Steve King (R-Ia.) follows through on his threat to sue the administration, his case will likely be thrown out in a heartbeat. The Court also confirmed that its Heckler ruling applies to immigration enforcement. In Reno v. American-Arab Anti-Discrimination Committee, 525 U.S. 471 (1999), the Court ruled that "in the deportation process, [a]t each stage the Executive has discretion to abandon the endeavor... many provisions of the [Illegal Immigration Reform and Immigrant Responsibility Act] are aimed at protecting the Executive's discretion from the courts -- indeed, that can fairly be said to be the theme of the legislation." While the administration's decision may have been "political," so was the decision to delay it. Officials delayed the move, not because they deemed it illegal, but because, according to a 2010 internal memo, "doing so would likely be controversial" -- despite the fact that deportation deferrals are not amnesty. "Prosecutorial discretion does not apply to affirmative acts of approval, or grants of benefits," Meissner noted in 2000. "For example, the INS has prosecutorial discretion not to place a removable alien in proceedings, but it does not have prosecutorial discretion to approve a naturalization application by an alien who is ineligible." Department of Homeland Security (DHS) Secretary Janet Napolitano understands this. As she wrote in her memo on the matter, "The use of prosecutorial discretion confers no substantive right, immigration status, or pathway to citizenship. Only the Congress, acting through its legislative authority, can confer these rights." In other words, her decision is not the Dream Act -- it does not in itself provide legal status -- which is why Mitt Romney has promised, if elected, to "work with Congress to put in place a long-term solution for the children of those that have come here illegally." Nonetheless, current law does allow individuals subject to deferred deportation to receive work permits if they can show "an economic necessity for employment." While there are no guarantees, it is likely many people will receive work permits. Far from undermining the "Rule of Law," the president has again simply executed the law as it was written by Congress. Immigration restrictionists may disagree with this particular use of prosecutorial discretion, but they don't disagree with its use on principle. When 60,000 Alabama businesses missed their state's deadline to sign up for E-Verify -- the employment verification program designed to catch undocumented workers -- the state extended to them a temporary amnesty. Alabama DHS spokeswoman Katheryn Kennedy said, "Right now we're not penalizing businesses. We're trying to help them, to be a safe harbor." In other words, even immigration restrictionists understand the practical importance of prosecutorial discretion. America has an undocumented immigrant population of between 10 and 12 million people -- this decision affects barely ten percent of that (1.4 million). Focusing on criminals and repeat border-crossers rather than people who through no fault of their own were brought here as children is sound policy given the scale of the issue. The idea that this order means the president is not enforcing immigration laws when he has deported a record 1.2 million people in his first three years in office is self-evidently absurd. Prosecutorial discretion plays an important role in responsible enforcement -- a role acknowledged in the immigration laws Congress passed. If Congress wants to revisit the discretionary powers it has vested to the executive, it is free to do so. Until then, restrictionists will just have to deal with a few more immigrants picking vegetables, starting businesses, and providing services that benefit all Americans.