A South Australian Supreme Court has ruled in favour of independent brewer Coopers in its fight with Lion Nathan over a clause in Coopers constitution that gives its larger rival rights to buy its shares.

Lion Nathan's third-tier pre-emptive rights allows it to acquire Coopers shares when they are offered for sale but not acquired by existing shareholders or the Cooper's superannuation fund.

Lion was granted those rights in 1995 in exchange for a 19.9% stake in Coopers, which Lion Nathan owned following its acquisition in 1993 of the South Australian Brewing Company.

Justice John Perry ruled that since the clause was first written, Lion Nathan's business structure had changed following the acquisition by Japanese brewer Kirin of a 46% stake in Lion Nathan.

Lion Nathan yesterday launched a takeover bid for Coopers Brewery.

The board of Coopers Brewery is expected to meet soon to discuss the ruling and how it will affect the takeover attempt.

Coopers' managing director, Tim Cooper, welcomed the decision but said it might not help fight off Lion's acquisition plans.

Lion Nathan has said it will appeal the ruling.