In another blow to the Trump administration’s policies on immigration, a federal court on Monday blocked the systematic detention of migrants who have shown credible evidence that they were fleeing persecution in their home countries.

In a sharply worded ruling, Judge James Boasberg of the Federal District Court for the District of Columbia found that the government’s own directive calling for asylum applicants to be freed when appropriate while their cases are pending “has been honored more in the breach than the observance.”

At issue is the right of those seeking shelter in the United States to be released while their applications for asylum are making their way through the courts, a process that can take years. While the government is entitled to hold them in detention, a 2009 directive provides that those who have shown what is known as a “credible fear” in an initial interview have a right to be considered for release.

In a court challenge, lawyers for nine plaintiffs who had been held in detention presented evidence that parole rates under the Trump administration have plummeted more than 90 percent to “nearly zero,” a shift they attributed to the government’s new “zero-tolerance” policy on immigration and an attempt to deter would-be asylum seekers from traveling to the United States and making a claim.