Labor unions were established to ensure reasonably high wages and salaries for its members, but they have now gleefully hopped on the cheap labor express. For reasons exactly like this, former union leaders like Samuel Gompers and Cesar Chavez opposed open borders. They were aware that it would lead to declining wages for working people.
Unions who greet the influx of illegal immigrants and allow them to join their ranks will cause nothing but trouble and lead to poor wages for hard working union members. This is exactly why illegal immigrants are being pushed to join unions. When membership reaches critical mass from the influx of workers, the current union structure will be used to control the "proletariat" laborers in a similar fashion to how it was done in the former Soviet Union.
Tyler Eugene Gravitt