Brett Kavanaugh, President Donald Trump’s nominee for the U.S. Supreme Court, is not a fan of net neutrality.

The former clerk to Justice Anthony Kennedy and current D.C. Circuit Court justice issued a blistering dissent last year in a ruling upholding the Federal Communications Commission’s net neutrality rule, and said that even if Congress had passed a net neutrality law, it would have been unconstitutional.

Advocates of net neutrality argue that without such regulation, which requires ISPs to treat all internet traffic as equal, ISPs like AT&T, Comcast and Verizon could charge more for various activities, such as video streaming, which takes up more bandwidth. This would then create a tiered system and stifle the free flow of information, they argue.

In his dissent, Kavanaugh said that the Obama-era FCC rule was not authorized by Congress and undermines the government’s separation of powers. “The net neutrality rule is unlawful and must be vacated,” he wrote.

That rule was reversed by the FCC under President Trump in December. In January, 21 states including California, New York and Virginia filed suit in the federal appeals court in Washington against the FCC for its decision.

In the same dissent, Kavanaugh argued that net neutrality violates the First Amendment, “because the rule impermissibly infringes on the Internet service providers’ editorial discretion.” Meaning even if net neutrality was legislated, he would still find it unconstitutional.

That could be a problem for states looking to instate their own net neutrality legislation in the wake of the FCC’s decision, like in California, where such a bill is poised to pass. Oregon, Vermont and Washington have already enacted net neutrality legislation.

Kavanaugh could be approved by the Senate as soon as this autumn, if Senate Majority Leader Mitch McConnell gets his way.

A net neutrality case has not yet been brought before the Supreme Court, with the most significant decision so far being the very ruling Kavanaugh dissented against. It is unclear where exactly the other Supreme Court justices stand on the issue, but Kavanaugh has made his position known.

Disclosure: Comcast owns NBCUniversal, the parent company of CNBC and CNBC.com.