With respect to sections 63 and 64, the context is about the termination of an environmental assessment. The question is, under what circumstances is the termination of an environmental assessment appropriate? To say that it should be terminated when the responsible authority in section 63, and the minister in section 64 decides not to exercise the power, duty, or function that could permit the designated project to proceed, in my interpretation leads to a situation where an EA could be terminated even though there's still value in doing an environmental assessment.
If it is clear that the refusal to exercise the duty, power, or function would not permit the project to proceed; in other words, if the regulatory decision blocks the project, of course there's no point in doing the environmental assessment. By changing the wording from “would” to “could”, suggests it is uncertain whether or not the regulatory duty, power, or function would prevent the project from proceeding, yet we are still terminating the environmental assessment.