Can you please tell me the role and background of trade union in the U.S.? I find some problems in understanding the following passage
...The other major controversial area of the immigration bill is the farm worker program. Agricultural interests wanted to be able to bring workers into this country to harvest crops without being subjected to employer sanctions, but the trade unions opposed this section of the bill...
According to existing immigration law in force in USA no employer can employ a non native worker without observing the provisions of Employer Sanctions. The purported intent of Employer sanctions was to deter illegal immigration and to protect American jobs by targeting the demand for undocumented workers.
I think there is move to relax this provision in respect of firm workers in the over-all interest of Agricultural activities but this has been opposed by the trade unions by virtue of their right to speak or raise voice against any change which might jeopardise the interest of their member workers.