Should it be illegal to make retroactive laws?

Retroactive laws are already illegal in the United States,
at least in the case of criminal law.  This prohibition was put in place by the
Constitution, which prohibits any ex post facto laws.  These are
laws that punish a person for something that was not illegal when the person did
it.

In general, civil laws may be made retroactive.  This
practice should, in my opinion, be banned.  It does not seem to be in any way fair to
tell a person or a company that some action that they took in the past is now illegal or
that they will have to pay damages for something they did which was not
illegal.

Ex post facto laws are clearly unfair and should
not be allowed in any situation.