The war between the Trump administration and the federal judiciary on immigration has just opened up a whole new front.

Judge Emmet Sullivan of the DC District Court ordered the Trump administration to stop using a June ruling from then-Attorney General Jeff Sessions when determining when domestic and gang violence victims who entered the US without papers would be eligible to stay and apply for asylum. In the process, Sullivan took aim at one of the administration’s more innovative tactics: using a little-noticed power of the attorney general to set immigration court precedents that make it harder for immigrants to get legal status.

Sullivan is the same judge who rebuked former National Security Adviser Michael Flynn at a sentencing hearing Tuesday.

The case before Sullivan was brought on behalf of 12 asylum seekers who had been rejected in the initial asylum screening process, an interview with an asylum officer to determine whether they had a “credible fear” of persecution if returned to their home countries. The judge ordered the government not to deport any of the 12, and to bring back the ones who have already been deported.

He also ordered the government to revert to its pre-June 2018 asylum policy in all future credible fear screenings; the Trump administration is already asking the DC Circuit Court of Appeals to stop this part of Sullivan’s order from going into effect.

It’s not clear how big an impact the ruling will have, because it’s not clear how much the Sessions policy actually affected approval rates in credible fear screenings; the overwhelming majority of asylum seekers were still passing their screenings even after the policy went into effect. But Sullivan’s ruling is also a brushback pitch against the administration, warning it against aggressive use of a tactic — having the attorney general set immigration policy by setting binding immigration court precedent — that has not previously been controversial simply because it hasn’t been used very often.

Sullivan’s ruling forces the administration to keep the door open to victims of persecution by nonstate actors

The federal government is required to allow people to seek asylum if they’ve been persecuted on behalf of their race, religion, nationality, political opinion, or “membership in a particular social group.” The last term is obviously the most open to interpretation — and it’s the job of the immigration court system, overseen by the attorney general, to interpret it. Because immigration courts aren’t independent (they’re part of the executive branch rather than the judicial branch), the attorney general can review cases and even issue new, binding precedents on them.

Technically speaking, Sessions’s June ruling was just a denial of asylum to a specific Central American domestic violence survivor, which overturned an Obama-era precedent that said that Guatemalan women afraid to leave their domestic partners did not constitute a “particular social group” under asylum law. But Sessions went beyond that in articulating general principles by which asylum claims ought to be judged — both by immigration judges and by asylum officers (even though the latter are not part of the Department of Justice), and at both the final review of an asylum case and the initial credible fear screening.

Judge Sullivan has now ruled that parts of Sessions’s ruling went further than just interpreting existing law and constituted a new policy that went against what Congress intended when it wrote asylum law. In particular, he targeted Sessions’s instruction that victims of domestic or gang violence didn’t count as “persecuted” unless the government of their home country either condoned their persecution or was “completely helpless” to stop it.

Sullivan’s ruling treats the Sessions policy as a bigger change than the government says it was. Sullivan says Sessions’s statement that “in general,” victims of domestic and gang violence “will not qualify for asylum on the basis of” that violence is effectively a categorical ban on asylum claims from those groups — even though the actual standards set forth by Sessions’s order leave room for some claims of persecution from domestic abusers or gangs.

Indeed, it’s not clear whether Sessions’s ruling actually made that much of a difference in how asylum officers conducted credible fear screenings. The rate at which people passed their credible fear interviews (as opposed to being rejected) dipped slightly over the summer, from 88-90 percent over the months before Sessions’s ruling to 84-85 percent in June, July, and August. But by September 2018 (the last month statistics are available), it was back up to 90 percent.

There’s been a broader downward trend in the number of credible fear cases getting approved by immigration judges on appeal, after an initial denial from an asylum officer — but that dates back to the beginning of 2018 and is thus more likely the result of other DOJ policies that give judges less time to review cases.

That difference of 5 percent still accounts for a few hundred people a month — and given that the stakes of deporting someone back to a country where they’d be in danger are literally life or death, that’s not nothing. (It’s worth noting, though, that because this case wasn’t a class action, for complicated legal reasons, Sullivan can only order the government to return the 12 people who are officially part of the lawsuit — not everyone else who was deported because they failed their credible fear screenings on account of the Sessions policy.)

Sullivan’s ruling might ultimately be less important for its immediate impact than as a new front in the war between the executive and judicial branches on immigration. Over the course of the Trump administration — going back to the ruling against Trump’s first travel ban in early February — federal judges have been the single biggest obstacle to Trump’s immigration agenda. By doing so, they’ve taken a less deferential approach to the executive branch than the judiciary traditionally has — forcing the government to show that decisions were made in good faith, and using the president’s own statements to conclude that his administration’s policies were impermissible.

Many of the Trump administration’s most innovative tactics on immigration have been pushing on the soft parts of the immigration system — the parts where the executive branch has never had firm limits put on its power. The use of “self-referrals” to issue new immigration court precedents was perhaps the best example of this phenomenon. But now, it too is being subjected to the scrutiny of a judiciary that does not trust this administration to faithfully enforce the law.