Singh was personally sued for libel by the BCA in July 2008, and in May 2009 Mr Justice Eady ruled Singh's article as a statement of 'fact'. The new ruling determines that Singh can defend his writing as "fair comment" - rather than having to justify it as fact.
In the appeal hearing, the Lord Justice Chief Judge said he was "baffled" by the BCA's claim against Singh.
Speaking ahead of the ruling, Index on Censorship, which is partnering Sense About Science and English PEN in the libel reform campaign, said that "this ruling could have a defining effect not just on Singh's case, but on the entire concept of 'fair comment' in English libel law".
Eady's decision
Mr Justice Eady, asked about Singh at the opening of the new City University London Centre for Law, Justice and Journalism last month, said he was unable to discuss a particular case but that:
"The basic principle is pretty clear, in terms of scientific discussion and research, that there should be completely free and uninhibited communication between experts in the field and indeed the general public at large.
"The question arises whether or not, in a particular set of of circumstances, the boundary between comment and fact has been overstepped. That's a very central issue in that case. I don't want to get drawn into that because I've expressed my view in that case.
"I don't think there's great danger for scientific investigation. Everyone accepts, I think, that freedom of communication is vital in that context."
Simon Singh's case has been a central example in the call for libel reform by the coalition of Index on Censorship, English PEN and Sense About Science.
In October Singh said: "The uncertainties in the legal system are such that you can't ever be 70 per cent sure. You're then placing a £1 million bet with a 30 per cent chance of losing."
Last month he announced he would no longer write his Guardian column and would be concentrating on fighting his case and supporting the libel reform campaign.
Disclaimer: Journalism.co.uk has pledged its support to the Libel Reform campaign.
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