"Living wage" laws mandating $15 an hour pay rates in Los Angeles and SeaTac include language that "would, in effect, exempt unionized workplaces," a USA Today editorial notices. Says the editorial, "The real motivation appears to be to promote unionization. By getting cities to dramatically increase the minimum wage, unions can claim they are fighting on behalf of all workers. By including opt-out clauses for themselves, they can use these new laws as a weapon to pressure companies to unionize."
It's almost unbelievable that this would be a union bargaining approach with an employer: in essence, "Recognize our union and allow us to collect union dues from your employees, and in return, we'll give you access to an exemption in the law that allows you to pay a sub-minimum wage."