^ Actual court ruling which is linked in the article itself.
I find the article's headline misleading. The court ruled that a proposition that was passed by voters in California which classified these drivers as contractors was mostly constitutional and would be allowed to have the effect of law, noting that California's legislative branch was free to change the law if they had the requisite votes to do so.
It wasn't the court, but California voters, which decided these workers are contractors. The court simply ruled that this is something voters are allowed to decide (and that lawmakers can change if they so choose).