WASHINGTON, Feb 26 (Reuters) - The U.S. Supreme Court on Monday was set to hear arguments on the legality of Republican-backed laws in Florida and Texas that restrict the ability of social media platforms to curb content that these companies deem objectionable in a pair of cases that could reshape free speech rights in the digital age.

At issue is whether these 2021 state laws regulating content-moderation practices by large social media platforms violate the free speech protections for the companies under the U.S. Constitution's First Amendment. Lower courts split on the issue, blocking key provisions of Florida's law while upholding the Texas measure.

The laws were challenged by tech industry trade groups NetChoice and the Computer & Communications Industry Association (CCIA), whose members include Facebook parent Meta Platforms , Alphabet's Google, which owns YouTube, as well as TikTok and Snapchat owner Snap.

Neither law has gone into effect due to the litigation.

The justices must decide whether the First Amendment protects the editorial discretion of the social media platforms and prohibits governments from forcing companies to publish content against their will. The companies have said that without such discretion - including the ability to block or remove content or users, prioritize certain posts over others, or include additional context - their websites would be overrun with spam, bullying, extremism and hate speech.

Another issue for the justices is whether the state laws unlawfully burden the free speech rights of social media companies by requiring them to provide users with individualized explanations for certain content-moderation decisions, including the removal of posts from their platforms.

President Joe Biden's administration, which opposes the Florida and Texas laws, has argued that the content-moderation restrictions violate the First Amendment by forcing platforms to present and promote content they view as objectionable.

Officials from Florida and Texas have countered that the content-moderation actions by these companies fall outside the protection of the First Amendment because such conduct - which they deem "censorship" - is not itself speech.

Conservative critics of "Big Tech" companies have cited as an example of what they called censorship the decision by the platform previously called Twitter to suspend then-President Donald Trump shortly after the Jan. 6, 2021, attack on the U.S. Capitol by his supporters, with the company citing "the risk of further incitement of violence." Trump's account has since been reinstated under Elon Musk, who now owns the company that was renamed X.

In signing the law in 2021, Florida Governor Ron DeSantis said, "Many in our state have experienced censorship and other tyrannical behavior firsthand in Cuba and Venezuela. If Big Tech censors enforce rules inconsistently, to discriminate in favor of the dominant Silicon Valley ideology, they will now be held accountable."

Florida's law requires large platforms to "host some speech that they might otherwise prefer not to host" by prohibiting the censorship or banning of a political candidate or "journalistic enterprise."

Texas Governor Greg Abbott, in signing the law in 2021, said, "There is a dangerous movement by some social media companies to silence conservative ideas and values. This is wrong and we will not allow it in Texas."

The Texas law forbids social media companies with at least 50 million monthly active users from acting to "censor" users based on "viewpoint," and allows either users or the Texas attorney general to sue to enforce it.

Florida is seeking to revive its law after the Atlanta-based 11th U.S. Circuit Court of Appeals ruled largely against it. The industry groups are appealing a decision by the New Orleans-based 5th U.S. Circuit Court of Appeals upholding the Texas law, which the Supreme Court blocked at an earlier stage of the case, with liberal Justice Elena Kagan and three of the court's more conservative justices in dissent.

(Reporting by John Kruzel and Andrew Chung; Editing by Will Dunham)