A Texas law was sustained by a US appeals court on Friday, prohibiting large social media companies with at least 50 million monthly active users from censoring their users on account of "viewpoint".

The state's decision comes as an unprecedented measure that limits the tech industry's ability to micromanage accounts and discourses, something social media companies claim would allow their platforms to become a "stronghold of dangerous content".

Based in New Orleans, Louisiana, the 3-0 ruling by the 5th US Circuit Court of Appeals, is considered the groundwork that would lead to the US Supreme Court's ruling on the law, which conservatives and right-wing commentators expressed as critical to preventing "Big Tech" from censoring their views.

Judge Andrew Oldham, an appointee of former President Donald Trump, wrote in the ruling, which was passed by the state's Republican-led legislature and signed by its Republican governor: "Today we reject the idea that corporations have a freewheeling First Amendment right to censor what people say". 

The tech groups concerned in the ruling - and thus recorded a legal loss on Friday - included NetChoice and the Computer & Communications Industry Association, which count Meta Platforms' (META.O) Facebook, Twitter (TWTR.N), and Alphabet Inc's (GOOGL.O) YouTube as members, which have sought to regulate user content when they believe it may incite violence, raising concerns that unregulated platforms will enable extremists such as Nazi supporters, terrorists, and hostile foreign governments.

The Computer & Communications Industry Association on Friday expressed its dismay with forcing private companies to provide equal treatment to all viewpoints.

"'God Bless America' and 'Death to America' are both viewpoints, and it is unwise and unconstitutional for the state of Texas to compel a private business to treat those the same," it said in a statement, as some conservatives labeled the social media platforms' practices as abusive, pointing to Twitter's permanent suspension of former US President Donald Trump from the platform shortly after the Jan. 6, 2021, attack on the US Capitol by a mob of his supporters, after which Twitter had cited "the risk of further incitement of violence" as a reason.

The ruling allows either users or the Texas attorney general to sue to enforce the law, as the ruling was praised as a "massive victory for the constitution and free speech" by Texas Attorney General Ken Paxton.

The included parties have a stronger case for petitioning the Supreme Court to hear the matter due to the 5th Circuit ruling conflicts with part of a ruling by the 11th Circuit, which is based in Atlanta, and which has previously found in May that most of a similar Florida law violates the companies' free speech rights and thus cannot be implemented.