It's a good point. One can make the same argument with respect to canals. A canal is also an international river. Of course an international river is any movement of water across a boundary, the way it's defined in the International River Improvements Act. The International Boundary Waters Treaty Act takes a different view. It talks about rivers in their natural channel. The two acts treat water differently in that respect.
I would say that when you're talking about pipelines or canals, it is a grey area of international law. I assume the government is aware of that and is prepared to defend it under NAFTA. But certainly the argument can be made that the water has been captured when you put it into a pipeline. I take that point.