* Journalist Greenwald's partner to appeal court decision
* Judge says detention was legitimate, criticises Greenwald
* Greenwald accuses Britain of "waging war" on press
By Costas Pitas
LONDON, Feb 19 (Reuters) - Britain's High Court has quashed a legal challenge against the detention under anti-terrorism laws of the partner of Glenn Greenwald, the journalist who brought leaks from former U.S. spy agency contractor Edward Snowden to world attention.
David Miranda had asked the court to rule on the legality of his detention and nine-hour questioning under terrorism legislation last August when he landed at London's Heathrow Airport en route from Berlin to Rio De Janeiro, Brazil.
He had argued that such detentions would have "an inevitable chilling effect on journalistic expression".
British authorities seized items from Miranda which they said included electronic media containing 58,000 documents from the U.S. National Security Agency (NSA), Snowden's former employer, and from its British counterpart, Government Communications Headquarters (GCHQ).
The High Court ruled on Wednesday that the detention of the partner of the ex-Guardian newspaper journalist was lawful and that anti-terrorism laws were correctly used.
"In my judgment the Schedule 7 (of the Terrorism Act) stop was a proportionate measure in the circumstances," said Judge John Laws.
"Its objective was not only legitimate but very pressing."
Schedule 7 allows for individuals to be stopped, detained for up to nine hours and have their items confiscated as they travel through ports and airports in order to determine whether they are involved in planning terrorist acts.
Civil liberty activists argue that certain groups such as Muslims are more likely to be stopped and Amnesty International has criticised Schedule 7 for being an "extremely broad law" that allows the abuse of individual rights due to its vagueness.
Miranda's lawyers said they had applied for permission to appeal against Wednesday's decision and that the judgement endangered journalism dealing with issues of national security.
"Journalism is currently at risk of being conflated with terrorism," said lawyer Gwendolen Morgan.
"Therefore our client has no option but to appeal."
'BRITISH WAR ON PRESS FREEDOM'
The ruling also criticised Greenwald's evidence that journalists share with government the responsibility to decide what should not be published to protect national security.
"Journalists have no such constitutional responsibility," the ruling said.
"The journalist will have his own take or focus on what serves the public interest, for which he is not answerable to the public through parliament."
Revelations by Snowden set off an international furore when he told newspapers last June that the NSA was mining the personal data of users of Google , Facebook, Skype and other U.S. companies under a secret programme codenamed Prism.
Further leaks from the former NSA contractor, who faces espionage charges at home and has temporary asylum in Russia, suggested the United States had monitored phone conversations of some 35 world leaders, including Germany's Angela Merkel.
The flood of accusations prompted U.S. President Barack Obama to announce reforms in January to scale back the NSA programme and to ban eavesdropping on the leaders of close friends and allies of the United States.
In Britain, a government official told the High Court last August Snowden's leaks had damaged British national security. The official said the data given to journalists included information that might expose the identities of British spies.
Home Secretary (interior minister) Theresa May welcomed Wednesday's decision and said that powers in place were fair.
"If the police believe any individual is in possession of highly sensitive stolen information that would aid terrorism, then they should act," May said in a statement.
In an online article, Greenwald, an American who now lives in Brazil, criticised the judgement and accused Britain of fearing public debate and oppressing reporters.
"It should surprise nobody that the U.K. is not merely included in, but is one of the leaders of, this group of nations which regularly wages war on basic press freedoms," he said.