gerryH:
If Iran blocked the straight, forcing the u.s.'s hand and the u.s. and their allies invaded. Where would you stand?
It would depend on context and our obligations.
Canada does not have a NATO obligation to get involved in a dispute between the US/Israel and Iran. If the US or Israel attack Iran (an act of war) and Iran closes the strait, Canada should condemn the US/Israeli attack and not get involved. As per rules of war, Iran would have a right to close the gulf.
If the US closed down the strait to Iran and its trading partners, then Iran can close the strait down to the US and its trading partners. Canada should not intervene or choose sides. We should try to remain neutral and avoid sending ships to region.
If Iran mined the gulf illegally closing the strait, then I support Canadians intervening to clear to strait at the request of our trading partners in the region and under UN authority.
If Iran illegally, unilaterally and militarily closed down the strait, with no justification, then its up to nations which have an interest in the region to decide what to do. Canada would have no NATO obligation to pick sides in this conflict. I'd support Canada putting its interests first. While a closed Persian Gulf might have a big negative impact on the rest of the world, Canada would see a net benefit. Canada owns the world's largest proven oil reserve outside of the gulf. Israel is not part of NATO. Israel's fight with the entire Muslim world and most of the middle east isn't our fight. Israel's problems with Iran aren't any more Canada's business than India's problems with Pakistan. I'd support Canada acting pragmatically to the benefit of Canadians, especially Canadians who work in Canada's oil industry. I'd support massive government intervention to build oil infrastructure to the West Coast.
If anyone attacks the American in the US or Europeans in Europe, then I support Canada acting as per its NATO obligations. Iran and their allies have an interest in not taking this conflict to Europe or the US.
If the war goes badly for Israel, I support opening Canada up to Israeli refugees.