I do not think that the courts have accepted that proportionality can be a challenge by way of judicial review where you are not raising an issue of EU law or convention law—but we have come a very long way towards recognising proportionality as a principle of the common law. That is one reason why I am asking this very important question. I simply do not know whether you can challenge retained EU law after exit day by reference to traditional common law principles.
One reason why this matters is that the Supreme Court, in the HS2 case, suggested that this might be possible under existing law. As was raised in the debate last Monday, we should also bear in mind that, under Clause 2, retained EU law includes statutory instruments that do not owe their legal basis to the European Communities Act. They include statutory instruments enacted through other mechanisms, albeit that they are linked to EU law. At present, one can challenge those instruments by reference to traditional common law principles. Therefore, if Clause 1(1) were intended to prevent such a challenge after exit day, it would be a significant change in the law.