If you listen to one top Democratic senator, Secretary of Education Betsy DeVos has pledged to make sure schools participating in a proposed federally backed school choice program must follow federal special education law. But the issue isn’t necessarily so straightforward.

Sen. Patty Murray, D-Wash., the ranking member of the Senate education committee, thinks DeVos made the answer pretty clear. On Tuesday, she asked DeVos if the $250 million school choice program in President Donald Trump’s proposed budget would require participating schools “to comply with IDEA.” (That’s a reference to the Individuals With Disabilities Education Act, the federal law governing programs for special-needs students.) DeVos replied, “Absolutely.” Watch that exchange below:

An aide to Murray subsequently said this amounted to a commitment that “all students in schools receiving federal funds should be protected under our nation’s civil rights laws, including the full range of Title IX and IDEA.” In other words, Murray believes DeVos has pledged that schools using federally funded vouchers would have to follow IDEA.

But can DeVos make that promise and have it backed up by the law itself right now?

The short answer is no. As our colleague Christina Samuels wrote recently, “Federal law states that parents who choose to enroll their children in private schools do not receive the Individuals with Disabilities Act protections that are granted to public school students.” And right now, states as a general rule do not require private schools participating in state-run voucher programs to follow IDEA.

We don’t yet know the exact legal structure of the $250 million program proposed by the Trump administration—indeed, DeVos said there is no “specific proposal” under that line item in the spending blueprint. But if any federal voucher program is to require private schools to follow IDEA, that would require either a direct change to the law outside the budget process, or change to the language in a congressional appropriations bill funding the Education Department. In the latter scenario, the Trump administration could propose such language, but only Congress could adopt it.

And either proposition would face a very steep uphill climb in Congress. DeVos said during the hearing said that her department would not issue “decrees” on which students are or are not covered under civil rights laws without congressional and court decisions on those outstanding issues.

In fact, some might argue that private schools shouldn’t have to follow IDEA, in part because there are no federal dollars flowing their way under the law.

And here it’s worth pointing out that IDEA is about eight years overdue for reauthorization by federal lawmakers. The law was last reauthorized in 2004, and has been overdue for reauthorization since 2009. Any reauthorization could include a requirement for private schools to follow IDEA. So far, there’s been little interest expressed so far this Congress in taking a fresh look at the law.

So irrespective of DeVos’ pledge to Murray, it will probably take congressional action for her pledge to really have teeth.