Americans hoping for stronger data privacy protections may find a foe in Brett Kavanaugh, President Donald Trump’s nominee to replace Supreme Court Justice Anthony Kennedy.

As a justice on the U.S. Court of Appeals for the D.C. Circuit, he dissented against his colleagues’ 2017 decision to uphold net neutrality, the Obama-era regulation requiring internet service providers like Comcast, Verizon and AT&T to treat all internet traffic as equal. Net neutrality violates the First Amendment, he said, because the regulation “infringes on the Internet service providers’ editorial discretion.”

It is not entirely clear where Trump’s administration stands on regulation of big tech. Although the Federal Communications Commission under Trump has already reversed net neutrality, on Thursday the Department of Justice appealed a federal judge’s June decision allowing AT&T to acquire Time Warner.

If Kavanaugh is approved, he would be the second-youngest Supreme Court justice at the age of 53. He would likely have a hand in decisions regarding data regulation far beyond Trump’s administration.

Some legal experts believe Kavanaugh’s First Amendment argument against net neutrality could be applied to data more broadly, and possibly pit him against current and potential data privacy regulations.

According to Christopher Sprigman, a law professor at New York University who authored an amicus brief submitted to the D.C. Circuit in favor of net neutrality, Kavanaugh’s argument that ISPs have a First Amendment right to determine what data they transmit implies that the data itself is speech.

If that is the case, he said, then the providers could argue that selling user data to advertisers counts as “speech” also protected by the First Amendment. If that argument were accepted by the court, there would be an additional hurdle to enacting data privacy regulation.

“The government would have to show an important interest that they are pursuing narrowly,” Sprigman said, “and that just makes it much more difficult for the government to regulate it.”

If Kavanaugh takes this position, it could spell trouble for state efforts to legislate data privacy protections if they were challenged in the Supreme Court.

Last month, California passed the country’s strongest law yeton data privacy. Starting in 2020, the law will require companies with data on more than 50,000 people to let consumers view data about themselves, request deletion of data, and opt out of having their data sold to third parties. Major tech companies like Google and Amazon opposed the measure.

Although the measure is popular, said Jane Bambauer, a law professor at the University of Arizona, it could be ripe for challenge in court.

“Because it affects so many different economic actors, and because it’s implicant this data as speech issue, I think it’s a really good example of a statute that was passed in sort of defiance of where the Supreme Court seems to be headed with its First Amendment doctrine,” she said.

Biometric privacy laws, which regulate the commercial use of physical identifiers such as iris scans and thumb prints, could also face trouble. Texas and Washington have such laws in place, but Illinois has the strictest, allowing individuals to sue companies.

As companies like Facebook make use of facial recognition technology, according to Bambauer, the definition of what exactly a biometric identifier is becomes a problem.

This could be a logistical challenge that gets solved through lobbying efforts, Bambauer said, or “it could be the sort of thing that companies choose to litigate and take advantage of First Amendment precedent to challenge the entire basis for the law.”

There is already some precedent for the idea that the court might view data as speech, according to Bambauer. A 2011 opinion struck down Vermont’s Prescription Confidentiality Law, which banned pharmacies from selling prescriber data to be used for marketing purposes without the prescribers’ consent, on the basis that it violated the First Amendment.

Kennedy wrote in the majority opinion that “this Court has held that the creation and dissemination of information are speech within the meaning of the First Amendment.”

Kavanaugh, who clerked for Kennedy, “would be likely, on these issues, to either replicate Kennedy or even steer further towards a First Amendment that’s more likely to degrade regulatory systems,” Bambauer said.

However, not everybody thinks that Kavanaugh’s position on data as speech is so clear. Geoffrey Manne, executive director of the International Center for Law & Economics, said that Kavanaugh’s position in the net neutrality case has more to do with the providers’ right to define their brand than the data itself.

The “editorial control” Kavanaugh references, according to Manne, is about ISPs deciding what content they provide customers. “It doesn’t have anything to do with the bits themselves,” he said.

Kavanaugh cited another reason, though, for opposing net neutrality. He said that the FCC’s initiation of the rule without authorization from Congress also rendered it unlawful. That position, according to Manne, is what could possibly pit Kavanaugh against regulations of data from the FCC and other agencies.

Even if data privacy regulations are struck down, Bambauer said, the biggest companies would still be held accountable. “They also have reputations to maintain, and that I think often matters more than the law on the books,” she said. “The court of public opinion can be much more punishing than regulators’ fines.”

That said, Facebook reached its all-time high in the stock market this week — four months after the Cambridge Analytica scandal came to light.

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