Government of Wales Bill

I want to understand a little more about the pre-legislative scrutiny. If I understand the Secretary of State’s position, the scrutiny will be on not the details of the legislation, but the principles of the area that will be delegated for the Assembly to legislate on. Does that not require a considerable abdication of the responsibility of Members of this House without the people of Wales endorsing that and saying that they would prefer the Assembly to do something, rather than hon. Members? How can the Secretary of State justify such a major constitutional shift without going to the people of Wales and asking them to endorse it by referendum?