Hypothetically, let's say an existing industry on the coast wanted to expand its operations such that it would require tanker shipments. It's possible that the exemption provision could be used by a minister to allow those industrial resupply exemptions. Obviously, many groups would argue against that.
Yes, it is to provide for certainty, in that the prohibitions of the act would in future—and as long as it is in force—ensure that oil tankers aren't being allowed into the region contrary to the purposes of the act.