That is an important point. I think that it was touched on in a previous question, and I apologise for not responding to it then.
Under the current system, if the Secretary of State expresses the view that a warrant should not be issued, it is open to the agency concerned to go away, reconsider, and then come back with more information about necessity and proportionality, or to abandon the warrant, or to consider applying for a different warrant. That process will continue to be possible under the new system.