Years ago, my brother taught in South Dakota when the union went after any teachers who “opted out.” He did anyway (Mom and Dad’s brood never lacked the stomach for a righteous fight), but he said most of the teachers just quit paying dues. It was just as effective. The union withered and died on the vine.
I think that was what got the teachers' union in Wisconsin all-a-twitter. Their dues were automatically deducted by the state and then Walker said they weren't going to do the unions accounting for them and shut it down. An en masse emigration ensued as the teachers followed the lead of their compatriots in ND.