I think the problem is that some, or even many, would have volunteered if not for the circulated letter. By collectively influencing each others' choices, rathe

I think the problem is that some, or even many, would have volunteered if not for the circulated letter. By collectively influencing each others' choices, rather than letting people choose individually without consideration from the union, the court ruled that this is essentially a union strike, especially since it had a purpose of trying to get benefits from the employer. And that could have been fine, but if I understand the article correctly, the problem is that there wasn't a vote on this action within the union. If it would have been voted on and formally taken as a union action, they would have been acting legally. But without the formal vote, it is an illegal strike according to the region's labor laws.