US radio host Alex Jones is suing PayPal, claiming bias against conservative views was behind its decision to block his website.
The conspiracy theorist has been banned from most major web services, including YouTube, Facebook and Twitter.
Mr Jones is alleging PayPal's ban is "viewpoint discrimination", calling it a "dangerous precedent".
PayPal told Courthouse News that the case was without merit and that it would vigorously defend itself.
PayPal decided to stop processing payments for InfoWars in September, claiming it violated their policies on promoting hate and violence.
The ban affected revenue Mr Jones made from selling Infowars-branded goods and right-wing literature.
"It is at this point well known that large tech companies, located primarily in Silicon Valley, are discriminating against politically conservative entities and individuals, including banning them from social media platforms such as Twitter, based solely on their political and ideological viewpoints," Mr Jones's company, Free Speech Systems, states in a 15-page complaint.
"Having effectively cornered the market, [PayPal] is now using that market power to restrain conservative trade and commerce," it adds.
Mr Jones is himself being sued over alleged defamation by the parents of two children killed in the 2012 Sandy Hook school shooting, which he has claimed was a hoax.