Now that Congress has gotten rid of the Obama administration’s accountability regulations for the Every Student Succeeds Act, the Trump-controlled Education Department technically can start the regulation process from scratch, but it is prohibited from writing “substantially similar” rules until new legislation is passed.

That begs two questions: One, will the Trump administration re-regulate? And two, what exactly would constitute “substantially similar” regulations to the Obama ones that Congress just tossed? (Spoiler: Congress may essentially get to decide whether any new Trump regulations are too much like the Obama regulations to pass muster. More below.)

On the first question—whether Team Trump will decide to come up with its own ESSA accountability regulations—we reached out to the department and haven’t heard back. It’s notable, though, that U.S. Secretary of Education Betsy DeVos sent a letter to state chiefs last month saying she would develop a template for ESSA plans and release it by March 13. (That’s Monday.) A new template isn’t the same as new regulations but since the Obama administration’s format got nixed with the rest of the regulations, the new format will provide some guidance.

So onto that second question. Let’s imagine that the DeVos and company decide that yes, they want to write new regulations, which could help provide clarity for states and districts on everything from how to handle schools where lots of kids opt out of standardized tests to the timeline for implementing different parts of the law.

Those new regulations can’t be “substantially similar” to the old Obama ones. But what exactly does substantially similar mean? And who decides what meets that threshold?

There doesn’t seem to be an easy answer to that question. Congress ditched the accountability regulations through a process known as the Congressional Review Act, or CRA, for short. Before this year, the CRA was only used one other time, to get rid of ergonomics regulations written by the Clinton administration. The courts haven’t had a chance to weigh in how it should work—and the law that created the CRA explicitly says there is no “judicial review.”

In fact, it may essentially be Congress that decides whether any new Trump-authored ESSA accountability regulations pass muster, by essentially passing yet another “disapproval” resolution like the one lawmakers just finished with, according to this report from the Congressional Research Service.

Or to put it a little more clearly: “We believe Congress ultimately decides whether a rule is ‘substantially similar’ to a rule that was overturned through the Congressional Review Act,” explained Brian Newell, the spokesman for the House education committee.

He noted that Republican lawmakers objected to the Obama administration’s rule because, in their view, it went beyond ESSA. (Democrats and many advocates for educators felt differently.) And he left the door open for the Trump administration to issue its own regulations.

“If the department were to move forward with a regulatory proposal in line with the law’s accountability provisions and the secretary’s authority, it’s hard to imagine anyone would argue that the new rule was ‘substantially similar’ to the old rule issued by the Obama administration,” Newell said.

One thing to keep in mind: Writing ESSA rules is no walk in the park. It’s a long and labor-intensive process. The Obama administration had to write draft regulations, solicit comments on them—there were more than 20,000 (!)—and then finalize them. That’s not something the Trump administration could do in the next three weeks, before the first batch of ESSA plans come due.