Read the original piece by TLC Legal Director Ilona Turner at Huffington Post Queer Voices.

On April 19, the Fourth Circuit Court of Appeals issued a precedent-setting decision for transgender high school student Gavin Grimm, resoundingly reversing a lower court decision that had held school districts can bar transgender students from using restrooms consistent with their gender identity.

The decision is a big win for Gavin, who can now continue his case in federal court. It is also game-changing for transgender people across the country, including the many transgender students who are facing this kind of discrimination daily.

And for the anti-transgender legislative attacks we’ve seen this year? As a practical legal matter, this decision likely spells their demise.

It all comes down to Title IX, the federal law that protects students from discrimination based on sex. The Fourth Circuit held that courts must defer to the U.S. Department of Education’s interpretation of Title IX, and the Department of Education has made clear that Title IX means transgender students have the right to be treated in accordance with their gender identity in all contexts. The appeals court also cited numerous decisions and guidance from other federal agencies in the last few years that have come to the same conclusion. Those decisions—such as the EEOC’s decision in Lusardi v. McHugh, brought by Transgender Law Center—have consistently held that transgender people must be permitted access to facilities like restrooms that match their gender identity.

While the Fourth Circuit decision will dramatically shift the legal landscape across the country, it holds particular importance for any future cases that will be heard in the Southern states that fall within the Fourth Circuit – including North Carolina, home of the vicious anti-trans law HB2, and South Carolina, which is currently considering a virtually identical bill.

North Carolina’s HB2 is already facing a federal lawsuit filed by Equality North Carolina, Lambda Legal, and the ACLU, which also represented Gavin Grimm. The federal district court in North Carolina, hearing that case, will now be required to follow the Fourth Circuit’s decision, since that decision is “binding precedent” on all courts within that circuit.

That means HB2, which forces schools to require transgender students to use restrooms based on the gender listed on their birth certificate, will almost certainly be struck down as a violation of federal law.

In South Carolina, meanwhile, Transgender Law Center is representing a transgender high school student who had been using the boys’ restroom since middle school, until this school year when a staff member realized that the sex on his records was listed as female. The school suddenly banned him from the boys’ restroom and suspended him when a teacher “caught” him using it.

While the proposed South Carolina law would enshrine the school’s discriminatory policy into state law, the Fourth Circuit decision makes clear that the school’s actions violated Title IX.

The lead sponsor of North Carolina’s HB2, Rep. Dan Bishop, said in an interview last month, “The whole nation ought to be watching” the Grimm case. He saw, rightly, that its outcome could determine whether laws like HB2 will survive legal challenges. Today it is clearer than ever that these laws will not stand.