> Among the practices prohibited by the Taft–Hartley act are jurisdictional strikes, wildcat strikes, solidarity or political strikes, secondary boycotts, secondary and mass picketing, closed shops, and monetary donations by unions to federal political campaigns. The amendments also allowed states to enact right-to-work laws banning union shops.
Labor in the US is weak by design.
What're they going to do, imprison the masses? Illegal doesn't mean much without realistic consequences.
But, usually the ruling class + capitalist class targeted those they identified as labor leaders (often with bogus charges-- even without evidence, these often ended in convictions. With some of these convictions resulting in the executions of innocent people).
But, just firing all workers who participate as was done in the 1980s when air traffic controllers attempted a strike would likely be sufficient to scare the working class back into compliance.
Or, for a larger action, you could punish the entire working class by sharply raising interest rates and inducing a recession. With the resulting large supply of unemployed/underemployed workers, labor will be too weak to make demands.