The Senate killed the bipartisan proposal to curb illegal immigration, but as President Biden’s Republican critics have suggested, he can, on his own authority, take measures that will limit the number of undocumented workers crossing the border.

If given sufficient fanfare, these measures could help Mr. Biden and the Democrats in November. They are also well worth doing for their own sake.

Still, those measures alone aren’t sufficient to put in place a long-term structure to bring order to the border and our immigration system. To do that, Congress also will eventually have to act.

Mr. Biden has authority to act under Section 212(f) of the 1952 Immigration and Nationality Act, which says that the president can “suspend the entry of all aliens or any class of aliens” whose entry he finds “would be detrimental to the interests of the United States.” In 2018, when the Supreme Court ruled in Trump v. Hawaii against challenges to the administration’s Muslim travel ban, it declared that this provision in the 1952 law “exudes deference to the President.”

Out of the more than three million attempted crossings by undocumented migrants at the southern border in fiscal year 2023, the roughly 2.5 million who got through have created a tremendous fiscal burden on our border as well as in cities and states not only in the Southwest but also in the Midwest and Northeast. Many of these migrants have joined an underclass of workers whom employers have over the decades exploited mercilessly to bring down wages in farming, meatpacking, construction and other vulnerable occupations. At the same time, the ease with which these undocumented migrants have gained passage has cast doubt on America as a nation of enforceable laws.

Using Section 212(f), Mr. Biden can narrow two of the main avenues through which the undocumented enter the country. While some migrants cross the border undetected — some 600,000 in fiscal year 2023 — or overstay visas, a much larger number now claim the right to asylum. In the Refugee Act of 1980, Congress put into law the United Nations convention for granting asylum to migrants who have a “well-founded fear of persecution on account of [their] race, religion, nationality, membership in a particular social group, or political opinion.”