The whistleblower site had been ordered to disable the domain after an earlier court ruled in favour of Swiss bank Juilus Baer which complained about leaked documents posted on the site.
Wikileaks was founded as an open forum for the anonymous posting of government and corporate documents.
The site has been host to incriminating documents regarding the Northern Rock crisis, human rights abuses in China, and political corruption in Kenya.
The San Francisco federal court decision overturns the previous ruling in which the site would have been forced to disconnect the wikileaks.org domain, cutting off the site's main URL.
The judge also overturned a restraining order preventing Wikileaks from running any Julius Baer documents on its site.
Defenders of Wikileaks, which included the American Civil Liberties Union and the Electronic Frontier Foundation, declared the decision a victory for free speech.
"We are very pleased that Judge White recognised the serious constitutional concerns raised by his earlier orders," said Matt Zimmerman, senior staff attorney at the Electronic Frontier Foundation.
"Attempting to interfere with the operation of an entire website because you have a dispute over some of its content is never the right approach."
Wikileaks back in action after reprieve
By Shaun Nichols on Mar 4, 2008 7:35AM