There was a difficult legal issue of retrospectivity and we had been given only a 50/50 opinion of success when we started, so I constantly wondered about the ethics of what the case was putting the women through and whether we should advise them to stop. (lawyer-monthly.com)
In short, there is an exception to the presumption against retrospectivity where there is (1) a statutory disqualification, (2) based on past conduct, (3) which demonstrates a continuing unfitness for the privilege in question. (thelitigator.ca)
As there is a presumption against retrospectivity where a vested or substantive right is affected. (criminalnotebook.ca)