A unionized cooperative is a cooperative, usually a worker cooperative, which is beholden to active legal involvement by trade unions in the representation of the worker-owners' interests. While they may be considered unnecessary in most cases, trade union involvement and membership may be welcomed by some cooperatives, be it to show voluntary solidarity with the organized labor movement's own history of struggle or to allow workers to negotiate collectively for the furtherance of workers' special interests within the more democratic and representative cooperative. This may be considered similar to the functions of political parties, special interests lobbies, and civil society pressure groups in democratic political systems.