Trade unions are organized groups of workers who engage in collective bargaining with employers. Some countries require unions and/or employers to follow particular procedures in pursuit of their goals. For example, some countries require that unions poll the membership to approve a strike or to approve using members' dues for political projects. Laws may govern the circumstances and procedures under which unions are formed. They may guarantee the right to join a union (banning employer discrimination), or remain silent in this respect. Some legal codes allow unions to obligate their members, such as the requirement to comply with a majority decision in a strike vote. Some restrict this, such as " right to work " legislation in parts of the United States.