A B.C. law banning discussion of class size from teacher contract negotiations has been struck down in court as an unconstitutional violation of freedom of association.

The 2002 legislation, introduced while Premier Christy Clark was provincial education minister, prohibited the subjects of class size, the number of special needs students in each class and workload from the collective bargaining process.

In a decision Wednesday, B.C. Supreme Court Justice Susan Griffin ruled that the law is a breach of the Charter of Rights and Freedoms.

"The government infringed teachers' freedom of association," Griffin wrote. "This infringement was not a reasonable limit demonstrably justified in a free and democratic society."

The judge gave the province one year to consider the repercussions of the ruling before the law will be officially declared invalid.

Clark told reporters that she hadn't yet read the decision, but said that government officials will look it over closely.

"We are going to take a little bit of time to review it," she said.

In her defence, Clark said that parents and school boards were in favour of the 2002 law, even if teachers weren't.

"We brought that bill in because we wanted to be sure the education system worked differently," she said. "There was a lot of support for the bill, but clearly it wasn't the right bill."

The B.C. Teachers' Federation called the decision a "tremendous victory" in a news release.

"Over the past decade, we have put tremendous effort and determination into the struggle to reassert our rights and regain the kind of teaching and learning conditions in our classrooms that we know students need and deserve, and today all those efforts are vindicated," BCTF President Susan Lambert said.

The union filed its suit against the government nine years ago, claiming that the legislation prevented teachers from negotiating on matters that have a substantial impact on working conditions.

The government countered that class size and composition are policy matters and should not be included in collective bargaining, claiming that it faced "labour unrest and virtual paralysis of the public school system" just before the law was enacted. Teachers were threatening to strike at the time and began staging partial job actions, refusing to participate in meetings or organize assemblies, shortly before the legislation was brought in.

But the judge ruled that the law -- brought in without consultation with the teachers' union and invalidating hundreds of terms in the collective agreement -- was too broad, and was not justified by looming labour troubles.

"The legislation undoubtedly was seen by teachers as evidence that the government did not respect them or consider them to be valued contributors to the education system, having excluded them from any freedom to associate to influence their working conditions," Griffin said.

"This was a seriously deleterious effect of the legislation, one adversely disproportionate to any salutary effects revealed by the evidence."

The ruling comes as B.C. teachers embark on negotiations for a new contract.