Unions in the US have a very specific legally-mandated structure. In the US, unions are required to represent a legally-defined "unit". Generally this constitu

Unions in the US have a very specific legally-mandated structure. In the US, unions are required to represent a legally-defined "unit". Generally this constitutes a group of workers with a well-defined role (e.g. line workers in a factory, butchers in a supermarket, graduate students in the UC system, teachers in California, etc.). When such a unit wishes to unionize, the members in the unit vote whether to establish a union. Assuming a sufficient number vote in favor, a union is formed that becomes the sole, exclusive, permanent (until dissolution) representative of all members of the unit during contract negotiations. This means that all members of the unit, including non-union members, are represented by the union for contract negotiations and it is illegal for anybody else, including yourself, to negotiate on your behalf (technically it is illegal for the business to negotiate with anybody other than the union, but this is functionally the same thing since any such agreement would be non-binding and then they would get fined for no benefit). In addition, no other union can legally be created that can represent any members of the unit. The only way to get different representation in such cases is to either dissolve the existing union or to vote out the leadership.