(AP Photo/Jacquelyn Martin)

This is very big news, not only because it could help determine the status of millions of undocumented immigrants whose fates are hanging in limbo, but also because it could thrust the immigration debate to the forefront right when the presidential race is hitting full boil:

The Supreme Court on Tuesday said it will decide whether President Obama has the authority to declare that millions of illegal immigrants be allowed to remain and work in the United States without fear of deportation. The court will probably hear the case in April, with a ruling before it adjourns in June….

Obama’s program, called Deferred Action for Parents of Americans and Lawful Permanent Residents (DAPA), would allow illegal immigrants in those categories to remain in the country and apply for work permits if they have been here for at least five years and have not committed felonies or repeated misdemeanors….But the executive action, taken after Congress failed to enact comprehensive immigration reform, was blocked by lower courts when Texas and 25 other Republican-led states sued to stop it.

There are several ways the Supreme Court could decide this dispute. It could agree with the administration that the states lack standing to sue, thus allowing DAPA to proceed. It could rule on statutory grounds — that is, on the question of whether Obama’s executive action is consistent with the Immigration and Nationality Act. The administration says that in the INA, Congress granted the executive a great deal of discretion to set enforcement priorities, and that DAPA — in temporarily deferring the deportation of millions of parents of children who are U.S. citizens or permanent residents, and allowing them to get work permits — is merely exercising this discretion.

The states have argued, among other things, that this executive action is tantamount to a broad policy change and thus required a “notice and comment” rule-making process. An appeals court agreed that the states have standing to sue and that they are right about the need for “notice and comment.” The Supreme Court could decide whether the appeals court is right based on an evaluation of either of those.

Or, thirdly, the Court could rule on the underlying Constitutional question. That’s because the Court took the unusual step of adding a question for the parties to argue: Whether Obama’s executive action “violates the Take Care Clause of the Constitution.”

Thus, the Court will hear arguments over whether, in instituting DAPA, Obama failed to “take care that the laws be faithfully executed.” It’s not clear whether those arguments will form the basis of the Court’s final decision, but they might. “The Court could say, ‘the statute doesn’t forbid what the president has done, so now we have to see what the Constitution says,'” Stephen Legomsky, an expert in immigration law at Washington University School of Law, tells me. (For Legomsky’s detailed arguments in favor of the administration’s position, go here.)

This could be very good news. Here’s why: Because it would be very useful to have the Court weigh in on the constitutionality of Obama’s executive action, given the all-consuming debate over whether Obama has regularly shown contempt for the Constitution, a case that is regularly made by Republicans who cite DAPA as a leading example of this.

The crux of the dispute over DAPA revolves around whether it constitutes an effort to “rewrite the law” (as opponents argue) or, rather, an effort to faithfully execute the law (as the administration and its defenders argue). Opponents argue that granting deportation relief to such a broad class of undocumented immigrants makes a mockery of routine prosecutorial discretion and constitutes unilateral lawmaking.

Defenders argue that the limited resources Congress appropriates for deportations — enough for 400,000 per year — require decisions to be made about who gets deported. The administration has laid down broad guidelines for making these decisions, prioritizing criminals, public safety threats and recent border crossers, and deprioritizing the removal of longtime residents with ties to communities and other categories. Opponents of DAPA don’t question the Constitutionality of such general guidelines in and of themselves. Rather, they say that DAPA oversteps by formalizing them with an official grant of temporary deportation relief and by granting beneficiaries work permits.

Defenders of DAPA counter that this act of formalization is perfectly consistent with both immigration statute and with typical exercises of prosecutorial discretion. They note that immigration statute already allows the executive to grant work permits to those who are granted deferred action status; DAPA simply broadens the category of those eligible for this deferred action status. What’s more, they say, this is only a temporary reprieve from deportation, can be revoked at any time, and only extends this formal reprieve to people who almost certainly aren’t going to get deported anyway. And in granting them work permits, DAPA lures them out of the shadows in which they’d remain anyway, which is good for enforcement and tax collection purposes. In the latter telling, then, with DAPA, the administration is actually executing the law faithfully and in the best interests of the country.

The question of whether DAPA represents faithful execution of the law or edges into unilateral, unconstitutional lawmaking is not an easy one to resolve. And resolution of it would be good for the debate and for the country.

Now, the politics: No matter what the Court decides in June, it will probably set off a bomb in the middle of the presidential election. Here’s why: If the Court allows DAPA to proceed, it will probably enrage the right and increase pressure on the GOP nominee — or the GOP candidates if there isn’t a nominee by then — to promise to reverse DAPA as president. Thus the GOP nominee may well end up redoubling his commitment to revoking the protection from deportation enjoyed by millions of immigrants. Alternatively, if DAPA is struck down, it will reignite the debate over what should be done about the millions of undocumented immigrants in this country. That could serve as a reminder that the GOP positions on this question range from proactive mass deportation (Donald Trump) to leaving them in the shadows and deporting them as the occasion arises (Ted Cruz) to maybe legalizing them at some undetermined point in the future once some undefined state of border security perfection is attained (Marco Rubio). And Republicans will be cheering the legal defeat of Obama’s efforts to shield millions from deportations.

Obviously Republicans might argue that this is a good debate for them — that swing voters don’t like Obama’s executive actions on behalf of immigrants and that it energizes the GOP base. Even if that is right, however, what will probably matter most for 2016 is how this battle colors the views of the two parties arrived upon by Latino voters. (Indeed, some GOP strategists clearly agree that this is the case, given their efforts to get the GOP to moderate on immigration.) And in that regard, whatever happens at the Court, it’s hard to see this debate playing in the GOP’s favor.