The difference between the Republican Party and the Democrats today is over the rule of law. When President Obama appointed judges without Senate approval, made environmental law without Congress, and rewrote his health law two dozen times, Republicans protested that Mr. Obama was shredding the Constitution.

Most Democratic lawmakers turned a blind eye to the Constitution they swore to uphold. Last Thursday, Mr. Obama opted for lawlessness again, dictating broad changes to immigration law. He made them banana-republic style: one man ruling with the stroke of his pen.

The phrase “banana republic” was invented by the American fiction writer O. Henry, in exile a century ago in Honduras. It was a country where laws were changed frequently by petty dictators. Mr. Obama says he’s acting alone because Congress waited too long. But the Constitution vests all legislative powers, including immigration and naturalization law, with Congress. It doesn’t say “unless Congress waits too long.” There’s no timetable.

Republicans are condemning Mr. Obama’s latest power grab. Predictably, only a handful of Democratic lawmakers have said they were worried about the president’s dictatorial approach. Most are applauding him for getting something done. The framers of the Constitution were worried about presidential power grabs. They were steeped in the history of European despots, and invented a system of checks and balances to keep power-hungry presidents in line.

The problem today is bigger than one lawless man. Democratic Party leaders – half of the nation’s political establishment – talk a lot about rights, but not about the rule of law. The Constitution isn’t on their radar. No matter where you stand on immigration, this growing indifference to the Constitution is alarming. It’s given Mr. Obama license to pursue his dangerous course and future presidents to do likewise.

Back in August 2013, Mr. Obama announced that he was delaying the Affordable Care Act’s employer mandate. A reporter asked him where he got the authority. “In a normal political environment,” he replied, “it would have been easier for me to simply call up the Speaker [of the House].” But he added that because Republicans controlled the House, he had to act without Congress.

Shockingly, our constitutional law teacher president forgot that having to share power with an opposing party is the norm. Nancy Pelosi defended Mr. Obama’s lawless act, saying it would help employers. The lone Democratic voice in Congress questioning the Obama administration’s announcement was Senator Harkin, the Iowa Democrat who will retire at the end of the 113th Senate. “How can they change the law?” he asked.

Now House Republicans are suing Mr. Obama over that mandate delay. Speaker Boehner says “no president should have the power to make laws on his or her own.” Mr. Obama laughs, saying he’s getting sued “for taking executive actions to help people.” In fact, he says, “middle class families can’t wait for Republicans in Congress to do stuff. So sue me.”

Worse, his fellow Democrats agree. Mrs. Pelosi calls the lawsuit “a distraction,” and the majority leader in the upper house, Senator Reid, labeled it a “show trial” that should be heard by Judge Judy. When the House debated the lawsuit, Democrat Louise Slaughter said it “makes no sense” for Republicans to demand enforcement of a law they don’t like. She’s not concerned about constitutional process.

George Washington would have shuddered. He warned that future presidents might try to expand their own power, in the name of doing good, but that’s how “free governments are destroyed.” President Obama is sure his immigration decree is smart politics. “We think people want results,” a White House flack said. “They’re more focused on outcomes than process.”

Not true. Last week’s NBC/Wall Street Journal poll showed that only 38% of people surveyed support the president’s going it alone to fix immigration, even though 57% support broad reform. Process matters to them. We Americans have the longest-functioning constitution in the world. That’s the essence of American exceptionalism, a concept that the president disputes but the Democratic Party would be foolish to discard.