AMERICA’S framers designed separate institutions to make, enforce and interpret laws. But as this week's Supreme Court hearing in an immigration showdown makes clear, the increasing dysfunction of Congress has provoked testy turf battles and confounding questions about the nature and limits of presidential power. Comprehensive legislation to reckon with 11.3m undocumented immigrants has eluded America for years. In November 2014, after the bipartisan, gang-of-eight Senate bill was foiled by the Republican leadership in the House of Representatives, Barack Obama picked up his pen and issued executive orders shielding about a third of the nation’s illegal immigrants from deportation and permitting them to work. On April 18th, the Supreme Court considered whether his actions were legal.

At issue in United States v Texas is Mr Obama’s move granting “deferred action” to undocumented aliens whose children are American citizens or lawful permanent residents. The policy, known as Deferred Action for Parents of Americans and Lawful Permanent Residents (DAPA), aims to grant relief to “hard-working people who have become integrated members of American society” and to keep families from being dispersed across international borders. The programme lifts the threat of removal from over 4m people but does not confer “any form of legal status” on its recipients and welcomes only law-abiding applicants who agree to submit to background checks.

Republicans in 26 states quickly condemned DAPA as executive overreach and won an injunction against it from a district-court judge in Texas, a ruling that was upheld by the Fifth Circuit court of appeals last November. In defending the policy at the Supreme Court, Donald Verrilli, the Solicitor General, noted the “pressing humanitarian concern in avoiding the breakup of families that contain US citizen children”. Since immigration officials have discretion over whom to deport, he said, and since the government “has resources only to remove a fraction of the unlawful aliens”, there is no legal barrier to prioritising the removal of some over others.

Scott Keller, the lawyer for Texas, found himself arguing in circles. In a master class in Socratic questioning, Justice Elena Kagan first got Mr Keller to admit that there is no legal problem with putting a hold on the deportations of select undocumented aliens. Then Mr Keller said that the states’ real complaint with DAPA is that it “grants a status” to its recipients. But Justice Kagan showed that in coming to this conclusion Mr Keller was mistakenly relying on the term “legal presence” in the DAPA memorandum. Referring to Mr Verrilli’s statement that it would be fine to “put a red pencil through it”, Justice Kagan reminded Mr Keller that “legal presence” is “just a label” with no “legal consequence”. If Texas objects to the fact that DAPA-protected immigrants are eligible to work, she said, it should direct its challenge elsewhere. “What you should be attacking is the work authorisation regulations that [government agencies have] had for 30 years”, she said, leading Mr Keller to feebly double back to his original claim: “I think it is DAPA itself that we're challenging.”

In a question to Mr Keller, Justice Stephen Breyer referred to the “tremendous political valence” colouring the immigration fight and suggested that it may have been cynically manufactured to get a hearing in court. The states’ supposed injury—having to pay for subsidised drivers’ licences of DAPA recipients—is a rather weak claim, Justice Breyer suggested, to “standing”, a constitutional requirement for all lawsuits. Permitting Texas to sue on fiscal grounds will lead “taxpayers all over the country” to sue “in all kinds of cases, many of which will involve nothing more than political disagreements” which courts are ill-equipped to adjudicate. “[B]efore you know it”, Justice Breyer warned, “power will be transferred from the president and the Congress, where power belongs, to a group of unelected judges.”

A dozen years before he became chief justice, John Roberts wrote that if the judiciary does not impose limits on the types of cases it hears, it risks “aggrandis[ing] itself . . . at the expense of one of the other branches”. But in his determined questioning of Mr Verrilli, Mr Roberts wasn’t buying the government’s argument that Texas suffered no real injury because it could decide not to pay for immigrants’ licences. Withdrawing that subsidy may subject Texas to lawsuits from immigrants claiming discrimination, he said. "[T]hat's a real catch-22”.

If, as it appears, the liberal and conservative justices are split evenly on both the legality of Mr Obama’s immigration policy and the standing question, a 4-to-4 divide will affirm the rulings in the lower courts. A tie will thus shelve DAPA indefinitely and disappoint millions of people who may have benefited from the programme. But even a win for the White House may be short-lived, giving potential DAPA applicants pause: both Donald Trump and Ted Cruz promise to reverse Mr Obama’s actions and clamp down on illegal immigrants if elected in November.