to collateral attack exception –
that availability of collateral attack could be restricted by statute.
charged with failing to take steps required by enforcement notice under
defence that decision to serve notice was ultra vires.
for court – was it possible to challenge administrative decision in criminal
case (ie make collateral attack on decision), or would he have to do it through
of Lords held it was open to Parliament to restrict such collateral challenges,
and question depended on construction of statute under which prosecution
might allow any public law claim to be raised collaterally by way of defence.
latter case, only formal validity of act was of relevance before court in a