>Or to put it the other way around:
>
>A law not enforced weakens two others.
>
>We have plenty of that ...

That is correct, when laws are not enforced, there can be a domino impact.

But that doesn't change the fact that the original rule was not enforced.

When laws are not enforced, there are usually 3 general reasons.

1) The legislation was badly written, too open to interpretation, and/or confusion about the law.
2) Those carrying out the laws do not understand their responsibilities, and/or make terrible mistakes (and that seems to have been the case for Dylann Roof)
3) Those responsible with executing the laws elect not to do so, for political reasons (and that is often the case with Barack Obama)