Twenty eight states within the U.S. are considered Right to Work states. But what does that actually mean, and how does it protect workers?

States that have passed Right to Work laws allow workers to choose whether to join their company’s union–or not. This not only keeps workers from paying steep union dues, but it gives them freedom of association.

States such as California, Illinois, and New York are not Right to Work states, and as a result, workers can be forced into signing union contracts or be bogged down with the fees and frustrations associated with workplace bargaining.

There have been efforts on both sides of the aisle to address Right to Work nationally. Last year, Senator Rand Paul (R-KY) reintroduced the National Right to Work Act, which would repeal six statutory provisions allowing private-sector workers, airline, and railroad employees to be fired if they don’t surrender part of their paycheck to a union. This effort ultimately failed.

On the other side, organizations such as the American Federation of Labor & Congress of Industrial Organizations (AFL-CIO)—who represent more than 12 million active and retired union members—call Right to Work “a policy designed to take away rights from working people,” and believe its purpose is to serve the needs of big corporations over individual workers.

Some states, including Tennessee, which has been a Right to Work state since 1947, are pushing to include Right to Work in their state constitution—ensuring these rights for Tennesseans both now and in the future. This follows states such as Alabama, who adopted Right to Work as a Constitutional Amendment in 2016 after being a Right to Work state since 1953.