WASHINGTON—A federal judge in Louisiana has issued a temporary restraining order against the Biden administration forbidding it from moving ahead with its plan to end Title 42, the pandemic-era border policy.

Judge Robert R. Summerhays, of the Western District of Louisiana, issued a temporary restraining order against the Biden administration on Wednesday after signaling his intention to do so two days earlier.

The Biden administration had been on track to end the policy on May 23, a decision that has come under intense criticism from Republicans and some vulnerable Democrats up for re-election this year.

The order prohibits the Homeland Security Department from taking steps to begin its wind-down of Title 42, such as opting to process more migrants using normal immigration channels ahead of May 23. The order doesn’t prohibit the administration from ending Title 42 on that date, though the judge, who was appointed by President Donald Trump, has set a hearing for a longer-lasting prohibition known as an injunction.

A Biden administration immigration official, asked Tuesday about the impending order, said the administration plans to comply with it but added, “We really disagree with the basic premise.”

A lawsuit brought by Arizona, Louisiana and several other Republican-led states alleged that the Biden administration had started reducing its use of Title 42 ahead of the May termination date and asked the judge to intervene urgently.

In response, a senior immigration official with the Homeland Security Department wrote in a court filing that the administration had specifically increased its use of expedited removal to deport single adults from Guatemala, Honduras and El Salvador.

Deporting a single adult using Title 42 or expedited removal is, in practice, similar. Under expedited removal, which is a normal immigration process, migrants are given a chance to request an initial asylum screening—most single adults fail it—before rapidly being deported. Once a person is deported, that deportation is recorded on the person’s record if he or she attempts to cross the border again, giving prosecutors a crime to prosecute.

Title 42, by contrast, eliminated formal consequences, and as a result single adults have been attempting to cross the border numerous times in hopes of gaining entry to the country without detection.

Write to Michelle Hackman at michelle.hackman+1@wsj.com