8 USC §1324b(a)(3)(B) makes it illegal for employers to discriminate against permanent residents, unless said permanent residents have failed to apply for naturalization within 6 months of becoming eligible.
So, if you are a green card holder who flips burgers at a fast food restaurant, is it illegal for your employer to fire you for making the choice to not apply for US citizenship, 6 months after you become eligible? Or, is there a separate statute that forbids such practice?