How could they not know they had broken a law of their own making?
Anyone who doubts that has only to look at the conduct of our current Government, which has sought to justify its existence by passing new laws without regard to the consequences.
Under Charlie McCreevy our tax system has become so convoluted that more and more people have to hire accountants to help them with their tax returns. Ask some of the established accountants and they will tell you that the Government has so complicated the system that they have had to hire extra staff just to prepare the returns, because they are no longer able to do so themselves.