Juan Tugoh,
I am no legal eagle, but my understanding is that the judge ruled that the impositions were not contractual changes. The company has to negotiate everything regarding contractual changes, and the ruling only said that the changes BA implemented were not contractual, so BA didn't have to negotiate them if they are considered reasonable. That doesn't make IA illegal, they still have the legal right to challenge it through industrial action. For example, it's not illegal for a company to close down a factory and move the production elsewhere cheaper, but it is still the legal right of the employees to fight against that through strike.