On Tuesday, the Associated Press reported that two previous Republican presidents—Ronald Reagan and George H.W. Bush—had taken unilateral action to protect undocumented immigrants from deportation, and the political reaction was much less vitriolic than what Obama has faced as he prepares to make a similar move. Conservatives, notably The Atlantic's David Frum and National Review's Mark Krikorian, quickly pushed back. Frum argues that, while legal, Obama’s upcoming executive action would be an unprecedented violation of political norms. Krikorian goes further, calling it "Caesarism, pure and simple." But in the end, though they difference in their vehemence, both Krikorian and Frum’s analyses do more to reveal the flaws in the conservative position than prove the lawlessness of Obama’s upcoming action.

Krikorian and Frum’s main argument is that Reagan and Bush’s unilateral actions were simply fixes to the 1986 immigration law that granted green cards to three million undocumented immigrants. Reagan and Bush discovered that, due to an unintended consequence of that law, many spouses and kids of newly-legalized immigrants faced deportation, potentially tearing families apart. In response, Reagan and Bush implemented “cleanup measures,” as Krikorian terms them: In 1987, Reagan’s Immigration and Naturalization Service announced that kids of newly-legalized immigrants would not be deported; Bush extended those protections to spouses in 1991.

According to Krikorian and Frum, these actions reflected Congress’s intentions because the legislative branch codified Reagan and Bush’s executive action into law in 1992. “Reagan and Bush acted in conjunction with Congress and in furtherance of a congressional purpose,” Frum writes. “Nobody wanted to deport the still-illegal husband of a newly legalized wife. Reagan’s (relatively small) and Bush’s (rather larger) executive actions tidied up these anomalies.” In other words, it would be unfair if Reagan and Bush deported children and spouses of newly-legalized immigrants. In fact, Bush’s executive action was called the “family fairness” program.

In contrast, they argue, Obama’s executive action is not what Congress intended. “A new order would not further a congressional purpose,” Frum writes. “It is intended to overpower and overmaster a recalcitrant Congress.” Krikorian was even more emphatic: “Whatever their merits, the Reagan and Bush measures were modest attempts at faithfully executing legislation duly enacted by Congress. Obama’s planned amnesty decree is Caesarism, pure and simple.”

What both Frum and Krikorian’s analyses fail to explain is how Obama’s planned action is not a faithful attempt at executing the law. You can’t argue that Obama’s “order would not further a congressional purpose” without explaining what Congress’s purposes are in passing immigration laws. This error isn’t unique to Frum or Krikorian: Conservatives often fail to use a legal framework in analyzing Obama’s action.

In August, I employed such a framework to explain why Obama’s executive action is legal because it's based on the idea of prosecutorial discretion—the federal government has only limited resources to implement laws and must prioritize them accordingly. But prosecutorial discretion has limits because Congress has the sole authority to write laws. If the president’s actions do not uphold Congress’s priorities—or, in Frum’s words, further a congressional purpose—it crosses the line into lawmaking.

A major priority of immigration law is deterrence. The more the federal government allows undocumented immigrants to stay and work legally in the United States, the more it incentivizes foreigners to come here illegally. That’s why conservatives see Obama’s executive actions as an unfaithful execution of the law. But Congress has other, competing priorities in passing legislation. They want laws to be uniform, predictable and fair, for instance. 

When the federal government implements immigration law, it must balance these priorities. In other words, the benefits of making the immigration system fairer must be greater than the costs of reducing deterrence. To an extent, of course, these are subjective judgments. But as long as Obama, or any president, for that matter, is implementing the law in line with congressional priorities—as I believe Obama is—his actions are legal.

In applying this framework to Obama’s upcoming executive action, the law supports the administration’s position. The change in immigration policy may remove a deterrent for foreigners considering illegally immigrating to the U.S. But the drop in deterrence is small, since the potential beneficiaries of Obama’s action must have lived in the U.S. continuously for many years. Foreigners cannot come into the country illegally under the expectation that the president will soon grant them protection from deportations.

On the other hand, the benefits of these actions are significant. They allow undocumented immigrants to come out of the shadows, work legally, and receive legal protections under U.S. law. They no longer have to worry about a discriminatory immigration system. Maybe most importantly, the new policy will prevent families from being torn apart—which was the main reason behind Reagan and Bush’s executive actions, which Frum and Krikorian believe was justified. 

It’s impossible to pick a specific point where the costs outweigh the benefits of Obama’s actions. As Obama shields more undocumented immigrants from deportation, the costs of the policy grow significantly. He risks crossing the line from upholding congressional priorities into lawmaking. But conservatives haven’t offered a legal framework to explain how Obama’s expected executive action crosses that line. Bush and Reagan’s actions were legally acceptable for the same reason Obama’s would be: ensuring that our immigration policy is fair.