WASHINGTON, March 15 (Reuters) - The U.S. Supreme Court

on Friday in a decision on free speech in the digital age set a

stringent new standard for determining if public officials acted

in a governmental capacity when blocking critics on social media

- a test to be applied in lawsuits accusing them of violating

the Constitution's First Amendment.

First Amendment protections for free speech generally

constrain government actors, not private individuals. Under the

new test, officials are considered engaging in governmental

action if they had "actual authority to speak on behalf of the

state on a particular matter" and "purported to exercise that

authority in the relevant posts."

The justices in a pair of unanimous rulings threw out

decisions by lower courts in cases from California and Michigan

involving lawsuits brought under the U.S. Constitution's First

Amendment by people who were blocked after posting criticisms on

the social media accounts of local officials.

The justices directed the lower courts to revisit the cases

based on the new standard.

Blocking users is a function often employed on social media

to stifle critics. The Supreme Court previously confronted the

issue in 2021 in litigation over former President Donald Trump's

effort to block critics on X, called Twitter at the time, but

failed to decide the matter by deeming the case moot after he

left office.

The Supreme Court heard arguments in two cases in October.

The first involved two public school board trustees from the

California city of Poway who appealed a lower court's ruling in

favor of parents who sued them after being blocked from the

accounts of the officials on X and Facebook, which is owned by

Meta Platforms ( META ).

The second case involved a Michigan man's appeal after a

lower court ruled against his lawsuit challenging a Port Huron

city official who blocked him on Facebook.

President Joe Biden's administration had sided with the

officials in both cases. Free speech advocacy groups urged the

justices to back the plaintiffs.

The California case involved Michelle O'Connor-Ratcliff and

T.J. Zane, elected trustees of the Poway Unified School

District. They blocked Christopher and Kimberly Garnier, the

parents of three students at district schools, after the couple

made hundreds of critical posts on issues including race and

school finances.

Zane and O'Connor-Ratcliff both had public Facebook pages

identifying them as government officials. The parents sued

O'Connor-Ratcliff and Zane in 2017, arguing that their free

speech rights under the First Amendment were violated.

A federal judge in California ruled that the parents' First

Amendment rights were violated and the San Francisco-based 9th

U.S. Circuit Court of Appeals agreed, ruling that Zane and

O'Connor-Ratcliff had presented their social media accounts as

"channels of communication with the public" about school board

business.

"When state actors enter that virtual world and invoke their

government status to create a forum for such expression," the

9th Circuit wrote, "the First Amendment enters with them."

In the Michigan case, Port Huron resident Kevin Lindke sued

in 2020 after City Manager James Freed blocked him from his

public Facebook page following critical posts related to the

COVID-19 pandemic. Lindke accused Freed of violating his First

Amendment rights. Freed's account also was a public Facebook

page identifying him as a public figure.

A federal judge ruled in favor of Freed in 2021 and the

Cincinnati-based 6th U.S. Circuit Court of Appeals last year

agreed. The 6th Circuit found that Freed's blocking of Lindke

did not constitute an official act.

The justices also are expected to issue rulings by the end

of June in other important cases involving speech on social

media. One involves a challenge to Republican-backed state laws

limiting the ability of social media platforms to remove or

moderate content deemed objectionable or misinformation. Another

involves a bid to prevent the Biden administration from

encouraging such content moderation.