The idea of anti-labor laws at the state level is to make belonging to unions less attractive. In Wisconsin, for example, the anti-union law that passed there in 2011 took away the rights of unions to collectively bargain for better pay and benefits for their members, while also eliminating automatic deductions for union dues. As a result, union members each month had to decide whether to write a check for a union that was no longer allowed to do much for members' bottom lines.
Since that law passed, membership in Wisconsin's two main teachers unions has fallen by a third. Over the weekend, the members of one union voted to consider merging with its rival. From the Wisconsin State Journal:
"It's about building local union power," Kenosha teacher Michael Orth said. "That's what we need to do."
You can see the unions' lost power is a few ways: declining membership, requirements that teachers pay more for their benefits, and the decimation of their ability to give money to candidates. The last part comes with direct political gain for Republicans, which helps to explain why Republicans like anti-union laws. Consider the biggest contributors nationwide in this cycle. The money from labor doesn't start to keep up with the money from business (read: Sheldon Adelson), but without it, the Democrats almost get shut out of the top 10.
(Image: The Overpass Light Brigade/Milwaukee)
Postscript: In September, a Dane County judge ruled that much of Wisconsin's anti-union law is unconstitutional. The decision affected teachers and Milwaukee public workers. Last month a law enforcement group with some members affected also sued.