Today most labor unions in the United States are members of one of two larger umbrella organizations: the American Federation of Labor-Congress of Industrial Organizations (AFL-CIO) or the Change to Win Federation, which split from the AFL-CIO in 2005. Both organizations advocate policies and legislation favorable to workers in the United States and Canada, and take an active role in Democratic party politics. The AFL-CIO is especially concerned with global trade issues.
Private sector union members are tightly regulated by the National Labor Relations Act (NLRA), passed in 1935. The law is overseen by the National Labor Relations Board (NLRB), part of the United States Department of Labor. Public sector unions are regulated partly by federal and partly by state laws. In general they have shown robust growth rates, for wages and working conditions are set through negotiations with elected local and state officials. The unions' political power thus comes into play, and of course the local government cannot threaten to move elsewhere, nor is there any threat from foreign competition. In California the public sector unions have been especially successful.
To join a union, workers must either:
be given voluntary recognition from their employer or
have a majority of workers in a "bargaining unit" vote for union representation.
In either case, the government must then certify the newly formed union.
Public sector worker unions are governed by labor laws and labor boards in each of the 50 states. Northern states typically model their laws and boards after the NLRA and the NLRB. In other states, public workers have no right to establish a union as a legal entity. (About 40% of public employees in the USA do not have the right to organize a legally established union.)
Once the union has won the support of a majority of the bargaining unit and is certified in a workplace, it has the sole authority to negotiate the conditions of employment.