Momentum is building behind the argument — now echoed even by Republican and conservative legal thinkers — that Obama is well within his authority to act unilaterally to shield many more people from deportations. Even opponents seem to concede the legal issues are not as clearly delineated in their favor as originally thought.

But opponents continue to argue that such a move — even if legal — would amount to a violation of political norms that could set a precedent for similar actions by a GOP president and generally hasten our spiral into nihilism.

The “political norms” argument must be taken seriously. But those making it here have not yet done so persuasively. The basic problem: The “political norms” case can’t neatly be untangled from underlying legal and policy disputes.

The starting point, I think, is this question: Does Obama’s deferred deportation program — and its expected expansion, which could impact millions — constitute a dramatic and substantial departure from the legitimate exercise of prosecutorial discretion that virtually everyone accepts as well within the president’s authority?

If the answer is No — as I hope to show — then the (non-rhetorical) question becomes: If the legitimate exercise of prosecutorial discretion over our deportation machinery does not amount to an intolerable affront to political norms, then why shouldn’t we conclude the same about deferred deportation programs?

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Opponents of Deferred Action for Childhood Arrivals — which protected from deportation certain categories of illegal immigrants brought here as children — and its expansion often describe them as an affirmative grant of quasi-legal-status to its beneficiaries.

But as Republican immigration law expert Margaret Stock explains, DACA and/or DACA 2.0 can also be understood as efforts to improve the implementation — for the good of law enforcement and the country — of enforcement priorities that most people already agree represent legitimate exercises of the executive’s discretion.

Opponents won’t concede this point. Their case against DACA and/or DACA 2.0 as illegal — or a violation of norms — turns heavily on the notion that such actions do represent a dramatic and substantial break from legitimate prosecutorial discretion.

The starting point for settling this is the “Morton Memo.” In 2011, the memo from the Director of U.S. Immigration and Customs Enforcement “identified ICE’s priorities for the apprehension, detention, and removal of aliens,” as a CRS report puts it. The memo instructs agents and lawyers to consider a range of factors — whether the person has a criminal history or poses a public safety threat, or has longtime ties to the community — in deciding whether to exercise discretion over removal.

This was in keeping with Obama’s refocusing of enforcement resources on serious criminal offenders and new border crossers, rather than low-level offenders who’ve been here a long time. Opponents of DACA object to those priorities on policy grounds but it’s hard to see Constitutional or serious “political norms” problems with them.

How different are such enforcement directives from DACA? Does DACA cross over into lawlessness or a reckless flouting of norms?

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In 2012, DHS announced DACA, which provided that individuals “will be eligible for an exercise of discretion, specifically deferred action, on a case by case basis,” if they came to the U.S. under the age of 16; have lived here for at least five years; are in school or are honorably discharged veterans; and have not been convicted of a felony or significant misdemeanor or don’t pose a public safety threat.

The argument that this is substantially different from legitimate prosecutorial discretion rests on the claim that a number of aspects of DACA and/or DACA 2.o push it over the “political norms” line. But as Republican lawyer Margaret Stock explains, these specific differences fall short of demonstrating that convincingly, and can easily be seen as an effort to improve the implementation of already-accepted-as-legitimate enforcement priorities:

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1) Opponents have argued DACA publicly exempts whole categories from prosecution, which could remove the deterrent effect of the law. But DACA only applies (as will its expected expansion) to people who have already been here for years. So it’s not clear how the public announcement of such priorities can provide an incentive to future lawbreaking. The Morton Memo (which most accept as legit) also in effect exempts whole categories in a similar fashion, laying out guidelines that deprioritize the deportation of people who meet certain criteria. DACA makes these categories more specific and precise — to encourage more uniform application.

DACA “creates specific criteria that people who don’t have lawyers can read,” Stock says, helping ensure that “individual bureaucrats don’t go off the reservation.” Says Stock: “It’s always good for the rule of law to have criteria for benefits clarified.”

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2) Opponents have argued DACA gives recipients the right to work and creates a bureaucratic process — including forms and fees — that amount to de facto temporary legal status. But presidential discretion to grant work permits to those whose deportations are deferred has long been enshrined in law, predating DACA, and this, too, amounts to an effort to better implement enforcement priorities in ways that benefit the country, as Shikha Dalmia explains:

Letting out-of-status foreigners stay is likely cheaper than deporting them. And if they are going to stay, it is far better to give them the legal means to earn their keep rather than seek handouts on the street or from the government.

What’s more, Stock adds, getting these folks into the light actually helps law enforcement: “It gets people on the record and allows government to do security checks into them it couldn’t before.”

Ross Douthat acknowledges work permits predate DACA, but complains DACA would make them available on a far grander scale. There is certainly something to this. But Stock points out that this discretion to grant work permits to deferred deportees was explicitly granted to the executive by Congress. Therefore, she notes, in the DACA context, it simply represents the president using powers granted by Congress to better implement enforcement criteria most already agree are legitimate. Opponents can understandably conclude the scale of this crosses a hidden line (more on this later), but it can’t reasonably be said to be “approaching a rewrite of the law.”

“Exercising statutory discretion doesn’t violate political norms — it’s taking care that the law is being faithfully executed,” says Stock. “Congress granted that discretion and Congress can always take it away.”

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3) Opponents argue DACA and/or DACA 2.0 are/would be effectively permanent policy that a future president wouldn’t dare reverse. I think President Ted Cruz would indeed reverse it on Day One, but this is a fair objection. The response: It does not reckon with the legal facts underpinning the actual status DACA grants, which remains at the discretion of the president, does not confer any new immigration status, and does not legally protect recipients should the government decide to remove them. As conservative Jonathan Adler notes, “the legal details matter.”

Indeed, the legal realities of DACA status are central to evaluating whether its creation violates political norms. DACA and/or DACA 2.0 would result in a shift in work status, but not nearly as great a legal shift as the one critics must claim to support allegations of law-rewriting or intolerable norm-flouting.

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4) Opponents argue DACA 2.0 would set a precedent for a future GOP president to decline to enforce laws in multiple other areas. Brian Beutler asks tough questions about whether DACA’s expansion would really set a precedent for any of this. Republican attorney Stock also offers a test for this claim: In any hypothetical case, has Congress granted the president the same sort of enforcement discretion in those areas that it has in the case of immigration?

“In a lot of these areas that people cite, Congress has not given the president the same broad discretion or statutory authority,” Stock says. “In immigration Congress has given presidents tremendous authority. It’s not setting a precedent for abuse when [a president is following] specific authority in the statute. An exercise of immigration authority doesn’t set a precedent [on] tax law authority.”

Here again, it’s impossible to disentangle the legal details from the argument over “political norms.” In the end, Stock’s basic argument is that DACA 2.0 would expand DACA in ways that are designed to better implement enforcement priorities that most already accept the president has the discretion to set.

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And yet we should concede expanding DACA does seem to press into uncharted territory. As opponents rightly note, Obama himself has said his authority is limited. This was probably about keeping pressure on Congress to pass legislative reform; indeed, it infuriated advocates who said he’d constrained his own authority in the quest for GOP support. Obama did say this, and it may now be politically harder to argue that whatever he does do isn’t the threat to political norms critics claim.

In the end, though, the question of whether DACA or DACA 2.0, whatever it looks like, amounts to a violation of norms has to be a subjective one. Douthat seems to agree: He says he can’t pinpoint the moment at which that line would be crossed. Similarly, while I’m more sympathetic to DACA 2.0, I wouldn’t want try to locate that line until I see what Obama proposes. I don’t know where the line is, either.

But perhaps the above offers a framework for evaluating whatever Obama does do. I suspect, though, that it will be hard to disentangle such evaluations from people’s policy inclinations. If you’re inclined against comprehensive reform, you’re more likely to see trappings like work permits as dramatic departures.

And yet some who are inclined towards comprehensive reform also seem inclined to believe Obama can do very little without crossing that hidden line. So, as Brian Beutler does, I’d invite them to consider the broader policy dilemma. Why should we only consider one set of consequences (DACA 2.0′s alleged impact on political norms)? Shouldn’t those who acknowledge presidential authority also weigh another set of consequences, i.e, of failing to exercise it and maintaining the status quo (lack of uniform policy; more deportations of longtime residents we already agree can be deprioritized; failure to extend them work authorization, which arguably has economic benefits; and failure to bring them out into the light, which helps law enforcement)?

If people do accept such prosecutorial discretion as legitimate, why do efforts to improve its implementation constitute an unacceptable affront to political norms, given that they confer a shift only in temporary work status — which Congress has authorized the executive to provide — and fall well short of new immigration status, let alone a suspension of enforcement of the law?

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.