These modes of change of tradition and morality in which
the law may be a causal factor must be distinguished from
legislative change or repeal. For though the acquisition or
loss of legal status due to enactment may indeed be spoken of
as the enacted statute's 'legal effect' this is not a contingent
causal change, as the statute's eventual effect on morals and
tradition is. This difference may be simply seen in the fact
that while it is always possible to doubt whether a clear,
valid, legal enactment will lead to a change in morals, no
similar doubts could be entertained as to whether a clear,
valid, legal enactment has changed the law.