> Sec. 211. (a) For the guidance and information of interested representatives of employers, employees, and the general public, the Bureau of Labor Statistics of the Department of Labor shall maintain a file of copies of all available collective bargaining agreements and other available agreements and actions thereunder settling or adjusting labor disputes. Such file shall be open to inspection under appropriate conditions prescribed by the Secretary of Labor, except that no specific information submitted in confidence shall be disclosed. - https://www.govinfo.gov/content/pkg/COMPS-8190/uslm/COMPS-81...
These are generally available from https://www.dol.gov/agencies/olms/regs/compliance/cba . Here's one such so-called "secret" agreement for "General Motors Corporation and International Union, United Automobile Aerospace and Agricultural Implement Workers of America (UAW) (2003)" at https://ecommons.cornell.edu/handle/1813/81116
So by your definition, the members of that union are not colluding.
Labor providers and labor consumers are not rivals, and they do not compete with each other.
You need to demonstrate how it is an "unfair market advantage". Simply saying it is so it not enough. It could be a fair market advantage.
"workers are rivals who are competing to sell labor to the market"
Ohh, that a funny one. You've just claimed that all trade associations are a form of collusion too.
The Orange Growers of Florida - made of rivals! - get together to promote Florida Oranges so are colluding to take market away from Californian orange growers. Well clutch my pearls!
You also think Microsoft is colluding with HCL, Accenture, TCS, and Chinasoft because Microsoft has negotiated a preferred status with them to find contract workers, rather than be open to the entire market of possible contract workers.
If it makes you feel better, think of the union as a co-op owned labor provider who made a multi-year contract with a company as the exclusive provider of a certain type of labor. Would that be "collusion"?
> when these workers agree not to compete
You've confused two different issues. 1) "workers are rivals who are competing to sell labor to the market" refers to all people who could be hired. Most of these people are not in a union, as we clearly see when the company hires scabs.
2) "A union occurs when these workers agree not to compete" generally refers to the people already working for a company. At least, I have not heard of a union started by people who were not employed and decided to use collective action to improve the market salary rate. Thus, they are not in the same market as #1.
The union for #2 acts as a single economic actor, just like you interpret the company as a single economic actor even though many managers may be involved ("collude") in setting new salary levels.