Covert Human Intelligence Sources (Criminal Conduct) Bill

Can the Minister explain one difference between the situation that has applied in the past and the situation that will apply in the future if the Bill goes through as it is? We are now legislating to make properly authorised criminal conduct lawful, rather than continuing with the current position whereby MI5 or another authorising authority is able to argue that it would not be in the public interest for prosecuting authorities to prosecute properly authorised criminal conduct, but there is no guarantee of immunity. What we are now saying is that they are not breaking the law, rather than, as in the past, that they were breaking the law, but that it was against the public interest to prosecute. Why the reason for that change?