As the Supreme Court staggers toward the end of its term, I keep thinking about a phrase quoted by the Chief Justice of the United States, John Roberts. He noted that when a president defies the express will of Congress, his power is at its “lowest ebb.”

Roberts was dissenting in the court’s decision in the so-called Jerusalem passport case. President Obama — and George W. Bush before him — had refused to execute a law that would’ve required listing Israel as the country of birth for an American born in Jerusalem.

The court let Mr. Obama deny the passport listing, but Chief Justice Roberts wrote that Mr. Obama’s power was at its lowest ebb. His point could serve as a marker for much of Obama’s entire tenure, which has often seen presidential power at its lowest ebb — or in a “zone of twilight.”

Both phrases are from a famous opinion written in 1952 by Justice Robert Jackson. He was writing about what he called “the actual art of governing.” This is the shortcoming that has hobbled Mr. Obama’s presidency — on ObamaCare, immigration, gun control, trade and Iran, to name but a few issues.

Jackson was an FDR liberal of the first water, but he understood presidential powers fluctuate depending on relations with Congress. Only with the “express or implied” authorization of Congress, he wrote, can a president be said to “personify the federal sovereignty.”

“Zone of twilight” was the phrase Jackson used to describe the predicament where a president acts “in absence of either a congressional grant or denial of authority,” meaning when Congress is quiet. Either the president or Congress might have the authority, but “its distribution is uncertain.”

A president’s power is at its “lowest ebb,” Jackson wrote, when he takes measures that are “incompatible with the expressed or implied will of Congress.” President Obama’s troubles stem from the frequency with which he has found himself in the twilight zone or at the low ebb.

The Jerusalem case is the least of it. The law the president defied may have been passed by an almost unanimous Congress, but the case was still about a child’s passport. A president skilled in the actual art of governing would’ve found a compromise.

There are bigger cases. The ObamaCare poser currently before the court should have been an easy fix, if it’s just, as the administration insists, about erroneous wording. Simply send it back to Congress for a rewrite.

It’s turned into a titanic drama because Congress wouldn’t come close to rewriting it the way the president wants. So he’s now crosswise with the legislature. On the centerpiece of his entire domestic program, he can’t personify the federal sovereignty.

The same is true for, say, gun control. The president wants to speak for the nation, but he’s without the support of Congress. So his latest gambit is to issue a regulation banning certain bullets that Congress won’t ban. He’s in the twilight zone.

On some issues — trade, metadata collection, immigration — conservatives like me may be with him. But Congress isn’t, at least not yet. Mr. Obama just can’t speak for the federal sovereignty. Nor take a hint. So he’s lurching around in the twilight zone, a weakened figure.

We’re likely to see this thrown into sharp relief if he gets his deal with the Iranian ayatollahs. Congress doesn’t like this appeasement. It’s made that clear. There may not be a veto-proof majority in Congress against him, however.

That’s what Jackson meant when he warned of acting against the “express or implied” will of Congress. The president, he wrote, has but “his own constitutional powers minus any constitutional powers of Congress.”

This doesn’t mean the president always loses. Mr. Obama defied the express will of Congress in, for example, refusing to enforce the Defense of Marriage Act. And he won. But it’ll be difficult for him to speak with the full federal sovereignty while the two branches are apart.

It’d be nice to think that whoever ends up as the next president will take this to heart. How wonderful it would be to have a president skilled enough in the actual art of governing as to speak with the authority of the full federal sovereignty.

This column first appeared in the New York Post.