I agree completely. Canada has the right and the duty to protect and control its inland waterways, and Prime Minister Harper deserves respect for taking this position. The United States Government is in the wrong on this.
American conservatives (rightly) scorned Canada for being unwilling to protect its national interests in the War on Terror. We should not now scorn Canada for being willing to protect its national interests at sea. Even if you believe Canada is in the wrong on this matter, it's still better than them gutlessly having no position at all.
I'll admit that I'm no expert here on International/maritime law. It would be interesting to know the facts. The bottom line with me is that we, Canada, establish some presence in the area to protect our interests and ultimately contribute to the protection and intelligence gathering of North America.