Without it, unions wield little power. Workers in any state can organize and lobby employers, but unions need the right to exclusively represent those employees and negotiate on their behalf to accomplish anything.
Moreover, the measure proposed by Gov. Scott Walker (R) and passed by the Legislature also makes public-sector union dues and membership voluntary, and requires workers to recertify the union every year.
"It's hard to see how a union could survive under those circumstances given how little they could contribute by collective bargaining," says Charles Franklin, a political scientist at the University of Wisconsin in Madison.