Those paragraphs of Humanae Vitae are NOT a discussion of what civil law SHOULD BE, but rather an exposition of how we discern what God's moral law IS.
Oh I see! The Encyclical was nothing but an intellectual exercise, a space filler?
Paul VI, nor any Pope, has any real interest in civil law. The Pope(s) are satisfied with the status quo and have no interest in civil law banning contraception?