The Secretary shall establish an annual goal for the purchase by each enterprise of mortgages on housing for low- and moderate-income families. The Secretary may establish separate specific subgoals within the goal under this section and such subgoals shall not be enforceable under the provisions of section
4566 of this title, any other provision of this chapter, or any provision of the Federal National Mortgage Association Charter Act [
12 U.S.C.
1716 et seq.] or the Federal Home Loan Mortgage Corporation Act [
12 U.S.C.
1451 et seq.].