No, IANAL, but my reading of the relevant law indicates that such an arrangement is illegal in the US. Unions in the US are legally enshrined as the exclusive r

No, IANAL, but my reading of the relevant law indicates that such an arrangement is illegal in the US. Unions in the US are legally enshrined as the exclusive representative of all members of a "unit" which has a precise legal definition which is approximately a group of non-management workers with a well-defined role (e.g. line workers in a factory, butchers in a supermarket, teachers in California) [1]. When a union is formed, all members of the unit are represented by the union including individuals who are not members of the union [2]. This also means that once a union is formed representing the unit, all non-official unions of the form you are suggesting are legally superseded by the official union. I believe this to be an accurate reading of the law as, as far as I am aware, there are no competing unions anywhere in the US unlike many countries in Europe which appear to have competing unions, though I am not particularly familiar with European labor markets. [1] https://www.nlrb.gov/guidance/key-reference-materials/national-labor-relations-act https://www.nlrb.gov/guidance/key-reference-materials/nation... Sec. 9 159 (b) [2] https://www.nlrb.gov/guidance/key-reference-materials/national-labor-relations-act https://www.nlrb.gov/guidance/key-reference-materials/nation... Sec. 9 159 (a)