A federal judge in Nashville ruled on Friday that there was a “realistic likelihood” that the indictment filed against Kilmar Armando Abrego Garcia, the immigrant who was wrongfully deported to El Salvador in March and then brought back to face criminal charges, amounted to a vindictive prosecution by the Justice Department.

The ruling was an astonishing rebuke of both the department and some of its top officials, including Todd Blanche, the deputy attorney general. Mr. Blanche was called out by name in the ruling for remarks he made about Mr. Abrego Garcia’s case on the same day in June he was returned to U.S. soil to face the charges in Federal District Court in Nashville.

In a 16-page decision, Judge Waverly D. Crenshaw Jr. said there was evidence that Mr. Abrego Garcia’s prosecution “may stem from retaliation” by the Justice Department and the Department of Homeland Security. Judge Crenshaw found that Trump officials may have sought to punish Mr. Abrego Garcia for having filed a lawsuit successfully challenging his initial “unlawful deportation” to El Salvador.

Moreover, Judge Crenshaw indicated how he was serious about getting to the bottom of the issue of vindictiveness. He said he intended to permit Mr. Abrego Garcia’s lawyers to pry, at least in part, into the Trump administration’s process of deciding to bring an indictment in the first place and how the charges related to the deportation case.

Vindictive prosecution motions are exceedingly difficult to win because of the high threshold required to prove that prosecutors acted improperly by filing criminal charges. Under the law, cases can be considered vindictive only if defendants can show that prosecutors displayed animus toward them while they were seeking to vindicate their rights in court, and that the charges would not have been brought except for the existence of that animus.

While Judge Crenshaw has not yet made a final decision on the issue of vindictiveness, the fact that he is even considering doing so in Mr. Abrego Garcia’s case is a hugely embarrassing blow to the Trump administration. From the moment Trump officials acknowledged that they had mistakenly expelled Mr. Abrego Garcia to El Salvador, President Trump and his top aides began a relentless barrage of attacks against him, calling him a violent member of the street gang MS-13, a wife beater and even a terrorist, effectively blaming him for being the victim of their own administrative error.