It's not. Hasn't been since 1947 (Taft-Hartley Act). Not sure why people keep saying it is. No American worker is required to join a union. They have the freedom to work wherever they want.

They also do not have to contribute financially to any union's political activities if they do not want to.

However, the union does provide a service through its collective bargaining power (on average: higher wages, better health coverage, better retirement benefits, better work rules, legal representation. You don't have to take my word for it. Lots of data out there from reputable non-partisan sources). Taft-Hartley also states that the union will provide that for EVERY SINGLE worker at the company, regardless of union membership. It does however state that even if you don't want to join the union or support its political activities (which again, has been EVERY SINGLE American's right since 1947) you do have to pay a fee for those services being provided to you, called an agency fee.

"Right-to-work" laws simply eliminate the agency fee. That's it. They don't have a thing to do with someone's right to work, which already exists. If these laws were completely about rugged, conservative individualism, and they stated that "you don't want to join a union or pay fees, no problem. You don't have to. You can be free to fend for yourself, and the union and its members can be free to do what they want for themselves," I'd be all about it. Knock yourselves out. But they aren't like that. That's not really the goal of these laws. It is to systematically erode the union's ability to function by making them provide all of the services/benefits to even those who do not contribute, which over time will be more and more people, reducing the union's ability to operate and achieve gains through a united, collective bargaining labor force (great for management and quarterly profits, by the way).

Every "right-to-work" law includes that one key, vital component, in that they come through on the first part (you don't have to join or pay fees), but they still force the union to provide you with all the benefits anyway. That is the crucial, insidious aspect of them, in that they allow people to receive something for nothing.