Accordingly, the legislation requires that agricultural employers recruit U.S. workers first, and that the terms of work offered foreign workers, when
Legislation requires that agricultural employers try to recruit U.S. workers first and if they still need workers then can open up employment to foreign workers. 
Legislation is not required to regulate employers to prevent large-scale moving of jobs overseas to foreign workers because companies will do the right thing and hire U.S. workers of their own volition. 