TOMMY Sheridan, the Scottish Socialist MSP, celebrated a legal victory yesterday when appeal court judges upheld his acquittal on a breach of the peace charge following a peace protest.

Anti-Trident campaigners said the decision raised doubts over hundreds of similar convictions and would force the police to rethink their tactics of mass arrests at peaceful protests.

Mr Sheridan, 38, had been charged with causing a breach of the peace at Faslane nuclear submarine base on the Clyde in February last year, when he was arrested along with 400 other demonstrators, including George Galloway MP, who was convicted.

He was found not guilty at Argyll and Bute District Court in Helensburgh last October, in line with an earlier landmark ruling that breach of the peace had to be ''more than irritating'' and ''must be genuinely alarming or disturbing in its context''.

An appeal by the Crown against his acquittal was rejected by the Court of Criminal Appeal in Edinburgh yesterday.

Outside the court, Mr Sheridan said justice had been done.

A Crown Office spokesman said the decision had been taken on its own facts and circumstances and had no implications for other cases.

However, David Mackenzie, of Trident Ploughshares, said: ''This puts the cat among the pigeons. There are more than 80 cases pending from Faslane blockades - what is the procurator-fiscal going to do with them? Acquittals in every case will be the only outcome.''