The law is not append-only. Bills can add and remove anything to/from the current body of law previously passed by the legislature (as distinct from the Consti

The law is not append-only. Bills can add and remove anything to/from the current body of law previously passed by the legislature (as distinct from the Constitution—there's a more complex procedure for ammending that—and as distinct from executive branch regulations—which can be effectively neutralized [requiring an executive rewrite] by legislation banning programs or actions or by denying funding, but Congress cannot directly rewrite exec regs). Congress rarely removes anything because there's rarely a benefit to the representatives to remove existing law. Special interests prefer exceptions carved out rather than striking out broad provisions that are currently active.