The Constitutional Court has upheld a judgment that holds trade union Satawu liable for a riot damage claim.

The court ruled on Wednesday the SA Transport and Allied Workers' Union (Satawu) was responsible for damages caused during a march in Cape Town in May 2006.

It found that the Regulation of Gatherings Act afforded victims effective recourse when a gathering became destructive and resulted in injury, loss of property, or life.

"The organisations are intimately involved in the planning, supervision, and execution of the gathering, but the potential victims are not," Chief Justice Mogoeng Mogoeng said in the ruling.

"Because of this, the organisations would be in a better position than innocent victims to identify individuals or institutions which caused the damage."

He said Satawu had the opportunity of a "soft landing" if it could track down those responsible for the damage caused during the protest and recoup its loss from them.

The majority of the court also held that the defence provided for by the law is viable and that the limitation on the right to freedom of assembly in section 17 of the Constitution was reasonable and justifiable.

Judge Chris Jafta, in a concurring judgment, said Satawu's appeal should be dismissed since it failed to prove that the law limits the right to freedom of assembly.

Satawu took the matter to the court after the Western Cape High Court found the union liable for the damages.

Several car owners and traders who were affected brought the claim.

The Supreme Court of Appeal upheld the High Court decision.

The damages were awarded under a provision of the Act, which creates a statutory liability on the part of organisations under whose auspices a demonstration was held.

Satawu had argued that the ruling and the wording of the Act would have a chilling effect on union members' rights to organise protests and demonstrations, as it would lead to financial ruin.

The respondents, including the then minister of safety and security, contended the provisions were consistent with the Constitution.

The City of Cape Town had joined as an intervening party and agreed with those sentiments.

The Freedom of Expression Institute sided with Satawu and were admitted as friends of the court.