IN ANNOUNCING he would phase out federal contracts for privately run prisons last month, President Biden delivered on half a campaign pledge but omitted the other, more difficult half — to also scrap privately operated migrant detention centers. And no wonder: While less than a tenth of federal inmates reside in privately managed prisons, the large majority of migrant detainees are housed in for-profit facilities, where they await adjudication in civil immigration courts.

The new administration’s wavering has disappointed immigrant advocates, who have rightly called attention to substandard and occasionally appalling conditions in detention centers run by contractors. As for Mr. Biden’s plans, the administration was deliberately vague. In a statement, the White House committed only to “take additional action in the future relating to the detention of undocumented immigrants.”

Given the vagaries in the future flow of unauthorized migrants, the administration’s own still-inchoate policy toward handling them and the potential of major fluctuations in the detainee population, perhaps it’s wise for the administration to proceed with caution. Still, the president’s instincts on the campaign trail were right and should remain the administration’s goal: For-profit detention facilities, where pre-pandemic problems have burgeoned into humanitarian danger zones during the covid-19 era, should be phased out.

That was the conclusion of the Homeland Security Advisory Council in the waning days of the Obama administration, which, on a majority vote, specifically rejected the idea that privately run detention centers under the aegis of Immigration and Customs Enforcement are imperfect but unavoidable. The panel acknowledged that housing migrants in such facilities is cost-effective and provides a means of accommodating surges in the number of detainees. Yet it also took note of the pattern of poor conditions and inadequate accountability in those detention centers, which it said justified a “measured but deliberate shift” away from privately run facilities.

Many of those centers were established over the past four years to accommodate the skyrocketing pre-pandemic population of migrant detainees arising from the Trump administration’s policies. Many of the facilities are in the Deep South, often in remote locations where access to emergency, specialized and other forms of medical care is inadequate. The result has been an array of reports, by media and advocacy watchdogs as well as the federal government’s own inspectors, that point to shabby treatment, often by staff who cannot communicate with detainees in their own language, and poor oversight.

The prevalence of covid-19, which spread all but unchecked in many privately run ICE facilities starting last spring, prompted authorities to release detainees or accelerate detentions. The detainee population, having peaked around 56,000 in 2019, has now dropped by more than two-thirds, to roughly 15,000.

That should make it easier for the government to intensify inspections in an effort to achieve more effective oversight of privately run detention centers. Yet it leaves unanswered the question of how the Biden administration will manage immigration enforcement generally, and detentions specifically, once the pandemic is tamed. What’s clear is that privately run detention facilities, having too often failed to provide humane conditions and quality medical care, need to go.