Julian Assange is to take legal action against the Ecuadorian government by accusing her of violating his "fundamental rights and freedoms".
The Wikileaks co-founder received a set of house rules from the embassy this week cleaning his bath and taking better care of his cat.
A memo threatened to confiscate the pet if he did not care for "well-being, food and hygiene".
Mr. Assange has been in the Embassy since 2012.
He has stayed there ever since he applied for asylum to prevent extradition to Sweden for rape – the investigation was later dropped.
Wikileaks lawyer Baltasar Garzon is in Ecuador to open the case that the Press Association expects to hear in court next week.
The organization said the country's government has threatened to remove Assange's protection by granting political asylum.
It added that his access to the outside world had been "cut short".
The embassy removed Mr. Assange's Internet connection in March, accusing him of "interfering in the affairs of other countries."
Earlier in the week, however, they said it would be partially restored.