This is from the Fed's 3/18/03 final rule amending Reg B:
Over the years, there has been concern that Regulation B generally does not apply to marketing through prescreened solicitations. When the regulation was originally implemented in 1975, the definition of ``credit transaction'' included ``solicitation of prospective applicants by advertising or other means.'' Thus, the prohibition against discrimination based on marital status and sex applied to solicitations. In December 1976--when Regulation B was revised to prohibit discrimination based on national origin, race, and other specified bases--the definition of credit transaction omitted any
reference to solicitations. In the final rule, the regulation instead prohibited creditors from discouraging persons on a prohibited basis from applying for credit.