>>25512904
It means unions can't force you to be part of them if you want to get a job in the factory. Murkan labor politics, and thus also industrial politics, was run by great lakes unions. Southern states gave a big fuck you to them when they started creating such laws, thus attracting industries looking for places not controlled by labor unions.
Labor unions like to pretend that they are the national working class and the national industries, nevermind that they are always geographically very clustered, because industries themselves are very clustered. Buy american meant basically buy great lakes. Southerners told them to fuck off with right to work laws.
To this day the rust belt cries saying that the new industries in the south didn't bring the south any wealth because they exploit the workers without protection, which is actually mostly true. But politically for southerners this is very much worth it, because at the least they weaken the north, who used to have national monopoly over industrial policies. Or at least it's a big middle finger for them.
We have same problem here in Brazil.