After years of debate and division, President Obama announced Thursday that he would use his executive powers to revamp the nation’s immigration system. But wait, you say, isn’t that Congress’ responsibility? Well, yes, it is, and if Congress had done its job, the nation wouldn’t be at this juncture. But here we are.

On the substance, the president is absolutely right. The immigration system is broken and unfair; it has resulted in a permanent class of illegal workers, it separates families and it denies a place in society to immigrants who work hard, pay taxes and have deep ties to the country. There are 11 million immigrants living in the United States without authorization and it makes practical and moral sense to legalize their status and offer them a path to citizenship.

But even though Congress has been discussing these issues for more than a decade, it has repeatedly failed, for reasons both political and substantive, to move a bill through both houses. A frustrated Obama finally announced — after initially saying he lacked the legal authority — that he would act on his own. His decision will, we hope, offer some breathing room to millions of immigrant families who have been living under the threat of deportation. But it also raises serious questions about the limits of executive authority.

Under Obama’s plan, the government will defer the deportation of parents of children who are U.S. citizens or legal permanent residents, if the parents have been in the country for five years. He will also expand the pool of so-called Dreamers — those who came to this country illegally as children — who are eligible for deferrals. He will not offer deferrals to their parents.

In all, some 5 million people could receive deferrals under the plan. Those who don’t have a criminal record will then be eligible for work permits. Obama also will expand the number of work visas available to foreign students graduating from U.S. colleges so that they aren’t forced to take their education and skills elsewhere.

People receiving deferrals will not be eligible for health coverage under the Affordable Care Act, nor will they qualify for other federal programs, such as food stamps, that support low-income citizens, permanent residents and others here legally.

Those are welcome changes, for the most part. But the process by which Obama achieved them is troubling on several fronts. We dislike the ease with which he shifted from saying he lacked the authority to act — to acting anyway. While most presidents use their executive powers from time to time — and Obama has done so to raise the minimum wage for federal contract workers and to protect federal employees from gender discrimination, among other things — his immigration plan is of a breadth and scale that may push the boundaries further than they’ve been pushed before. Liberals who approve of the president’s action should remember what they thought when George W. Bush claimed executive authority to act without congressional approval; they were not pleased by what they perceived as an end run around the rule of law.

Obama’s decision not to deport millions of people has been framed as an issue of “prosecutorial discretion,” but that seems disingenuous. Although it may be true that Congress has budgeted enough money for the Department of Homeland Security and the Department of Justice to remove only 400,000 illegal immigrants a year — out of the pool of more than 11 million — scarce resources and setting priorities are not the issues here. The president is seeking to enact a policy that he has been unsuccessful in persuading Congress to support.

That’s not how policy should be made.