The Supreme Court will hear arguments on Monday in a pair of cases that could fundamentally change discourse on the internet by defining, for the first time, what rights social media companies have to limit what their users can post.

The court’s decision, expected by June, will almost certainly be its most important statement on the scope of the First Amendment in the internet era, and it will have major political and economic implications. A ruling that tech platforms like Facebook, YouTube and TikTok have no editorial discretion to decide what posts to allow would expose users to a greater variety of viewpoints but almost certainly amplify the ugliest aspects of the digital age, including hate speech and disinformation.

That, in turn, could deal a blow to the platforms’ business models, which rely on curation to attract users and advertisers.

The laws’ supporters said they were an attempt to combat what they called Silicon Valley censorship, through which major social media companies had deleted posts expressing conservative views. The laws were prompted in part by the decisions of some platforms to bar President Donald J. Trump after the Jan. 6, 2021, attack on the Capitol.

The laws, from Florida and Texas, differ in their details. Florida’s prohibits the platforms from removing any content based on a user’s viewpoint, while Texas’ prevents the platforms from permanently barring candidates for political office in the state.

“To generalize just a bit,” Judge Andrew S. Oldham wrote in a decision upholding the Texas law, the Florida law “prohibits all censorship of some speakers,” while the one from Texas “prohibits some censorship of all speakers” when based on the views they express.

The two trade associations challenging the state laws — NetChoice and the Computer & Communications Industry Association — said that the actions Judge Oldham called censorship were editorial choices protected by the First Amendment, which generally prohibits government restrictions on speech based on content and viewpoint.

The groups said that social media companies were entitled to the same constitutional protections enjoyed by newspapers, which are generally free to publish what they like without government interference.

The states responded that internet platforms were common carriers required to transmit everyone’s messages and that the laws protected free speech by ensuring that users have access to many points of view.

Federal appeals courts reached conflicting conclusions in 2022 about the constitutionality of the two laws.

A unanimous three-judge panel of the U.S. Court of Appeals for the 11th Circuit largely upheld a preliminary injunction blocking Florida’s law.

“Social media platforms exercise editorial judgment that is inherently expressive,” Judge Kevin C. Newsom wrote for the panel. “When platforms choose to remove users or posts, deprioritize content in viewers’ feeds or search results or sanction breaches of their community standards, they engage in First Amendment-protected activity.”

But a divided three-judge panel of the Fifth Circuit reversed a lower court’s order blocking the Texas law.

“We reject the platforms’ attempt to extract a freewheeling censorship right from the Constitution’s free speech guarantee,” Judge Oldham wrote for the majority. “The platforms are not newspapers. Their censorship is not speech.”

The Biden administration supports the social media companies in the two cases, Moody v. NetChoice, No. 22-277, and NetChoice v. Paxton, No. 22-555.

The Supreme Court blocked the Texas law in 2022 while the case moved forward by a 5-to-4 vote, with an unusual coalition in dissent. The court’s three most conservative members — Justices Samuel A. Alito Jr., Clarence Thomas and Neil M. Gorsuch — filed a dissent saying they would have let the law go into effect. Justice Elena Kagan, a liberal, also dissented, though she did not join the dissent and gave no reasons of her own.

Justice Alito wrote that the issues were so novel and significant that the Supreme Court would have to consider them at some point. He added that he was skeptical of the argument that the social media companies have editorial discretion protected by the First Amendment the way newspapers and other traditional publishers do.

“It is not at all obvious,” he wrote, “how our existing precedents, which predate the age of the internet, should apply to large social media companies.”