https://www.flra.gov/exclusive_representation

http://www.hr.ucdavis.edu/elr/lr/collective-bargaining/ee_re...

The tl;dr of it is that if 50% + 1 of a workforce unionizes, the union bargains collectively for everyone. Even for free-loaders who don't pay union dues.

This is like being able to opt out of paying taxes, while still receiving all government benefits. If that were legal, then our public services would collapse by next week.