Sometime in late summer, if predictions are right, President Obama will use his executive authority to protect many unauthorized immigrants from deportation.

We don’t know the details. Mr. Obama and the Department of Homeland Security have not yet supplied the who, what, when or even, officially, whether. But Mr. Obama has promised to respond to Congress’s refusal to act on immigration reform. And the most obvious thing is to lift the threat of deportation from immigrants who should be the lowest priority for removal: those with citizen children, jobs, clean records and strong community ties. Some reports put the size of that group at four million to five million.

The mere possibility of Mr. Obama’s protecting any of the 11 million immigrants living here outside the law is already making Republicans clutch at their chests and cry out: Oh, the legality! He has done nothing yet, but right-wingers have pre-emptively declared him Caesar, crossing a Rubicon into lawlessness.

In truth, Mr. Obama is well within his authority to madden the right. His power to conduct immigration policy is vast. Congress has given the president broad flexibility and discretion to enforce immigration law. It has also given him the resources to deport about 350,000 to 400,000 people a year, as Mr. Obama has done, relentlessly. It could have given him billions more to deport everyone, but it has not.