A few pages into a consequential U.S. Supreme Court ruling Thursday on immigration policy, Chief Justice John Roberts, writing for the majority, quotes two of his predecessors on the matter of cutting corners.

"Justice Holmes famously wrote that '[m]en must turn square corners when they deal with the Government.' … But it is also true, particularly when so much is at stake, that 'the Government should turn square corners in dealing with the people.' "

Thursday's ruling finds that the Trump administration's Department of Homeland Security took shortcuts around the right angles of administrative law when it decided in 2017 to end Deferred Action for Childhood Arrivals, an Obama-era policy that, under specified conditions, delays the potential deportation of people who were brought into the country illegally as children and allows them to work and receive federal benefits.

Thus, DACA survives on a technicality. The court's 5-4 ruling sends the issue back to the lower courts, where DHS can try again to defend its plans. The three-quarters of a million people who have benefited from the policy have gotten a reprieve, but the ultimate paths of their lives still hang in the balance, especially if President Donald Trump wins a second term.

Much will be made of the fact that the court has delivered Trump two major defeats this week, Monday's decision on LGBT employment rights being the first. What Thursday's ruling really illustrates, however, is the peril of conducting major policy by executive order.

The dissenting justices argue that the Obama administration acted with as much caprice in implementing the policy in 2012 as the Trump administration did in rescinding it. That was, in fact, the basis under which Trump's first appointed attorney general, Jeff Sessions, declared DACA illegal — a determination even Roberts noted that DHS had to act upon, the question being how. (Moot point — illegal is illegal, wrote Justice Clarence Thomas for the dissenters.)

The country has now engaged in two decades of "policy, religious and moral debates about the legal status of millions of young immigrants," wrote Justice Brett Kavanaugh. Yet through all this, Congress has failed to act.

Those covered by the DACA policy fill essential roles in the workforce. They pay taxes. It's time for the legislative branch to turn a corner and give them the certainty they deserve.