Assange, who has been taking refuge in the Ecuadorian embassy in London since June 2012, said in a statement issued by WikiLeaks on Friday that his lawyers would challenge a "protocol" put in place by Ecuador that made it mandatory for his lawyers to hand over personal details before being allowed to see him.
The case was launched in Quito by WikiLeaks general counsel Balthazar Garcon who arrived in the Ecuadorian capital on Thursday.
The statement said: "The move comes almost seven months after Ecuador threatened to remove his protection and summarily cut off his access to the outside world, including by refusing to allow journalists and human rights organisations to see him, and installing three signal jammers in the embassy to prevent his phone calls and Internet access.
Assange has said that he fears being extradited to the US if he leaves the embassy in London. Last year US officials said arresting him was a top priority.
The WikiLeaks statement said: “The US case against Julian Assange dates back to the Obama administration 2010, but has been expanded under Trump to include the biggest leak in CIA history, Vault 7."
The statement said pressure had been increasing on Ecuador to hand Assange over to the UK, especially since US President Mike Pence's visit in June during which Ecuador President Lenin Moreno and Pence "agreed to remain in close co-ordination" in relation to Assange.
"Last week, Ecuador's former President Rafael Correa, under whose administration Assange obtained political asylum, said that the current administration is 'trying to break him psychologically' and that a deal had been struck during Pence's visit to Ecuador earlier this year," the statement claimed.
The protocol referred to earlier makes Assange's political asylum contingent on censoring his freedom of opinion, speech and association.
"The protocol also requires journalists, his lawyers and anyone else seeking to see Assange to disclose private or political details such as their social media usernames, the serial numbers and IMEI codes of their phones and tablets. The protocol says the government may share these details with other agencies. The protocol claims the embassy may seize Assange's property or his visitors, and, without a warrant, hand it over to UK authorities," the statement said.