orathiac, you are entirely biased by not knowing at all what you're talking about. As SantaClausowitz said, it is a transit passage, or international waterway. Every state, even landlocked ones, have the right to use it, just as they have a right to use the high seas. In addition to choking off the flow of oil out of the Gulf, it prevents Qatar, the UAE, Kuwait, and Iraq from accessing international waters. You can't do that. If it were permissible for a state to shut down these choke-points without repercussions then Spain and Egypt could turn the Mediterranean into a lake on a whim.
"that fact that a country allows international trade to go through their exclusive economic zone is like having a the US allow Mexicans to trade with Canadians without paying trade tariffs."
You simply don't know what an EEZ is. They give a state control of the resources in those waters, not control over what goes through them. For example, a state can lay claim to the fish and oil in its EEZ, but it cannot say that any ship passing through those waters on its way to another state has to pay taxes or ask permission to enter. Think for a minute how unworkable such a system would be. EEZs extend 200 miles offshore, for goodness sakes.
"Comparisons with the Israeli blockade of the Gaza strip spring to mind. This is considered legal under international law. (even if it causes suffering and starvation among the population of Gaza)"
It's no comparison at all. Israel is an occupying power in Gaza. As an occupying power it can legally impose a blockade. And at any rate, preventing direct shipments into Gaza is in no way comparable to Iran's cockamamie behavior here. That's no endorsement of Israel's actions, just a statement that we're dealing with issues which are similar only in that both involve boats.
"Meanwhile the only suffering that will be caused if oil shipments through the straits stop is some price rises that will hit wealthy consumers who already have enough to eat."
You can't be that stupid. Shutting down the strait could lead to a huge increase in oil prices, which means higher transportation costs, which mean higher prices for everything. Unless you live in a Unabomber hut in the mountains or are some Tuareg in the desert this would affect you, and affect you significantly. That's to say nothing about how it very well could spark a general war in the Middle East, leading to thousands of deaths at the very least.
"If the US wanted to stop the import of components non-nuclear missiles into Cuba, this too would be justified by you because it is so clearly in the US national interest."
It may be justified in a national security sense, but I've been talking about international law this whole time. Strictly speaking, no the United States would not be justified as a matter of international law in redoing Kennedy's quarantine just because we don't want Cuba to have missiles.
You're just wrong, orathiac. America has often been ham-fisted when it comes to Iran and has been far from saintly (we're almost certainly behind the recent bombings and assassinations there), but in this particular case where it comes to Iran threatening to close the strait, we are completely in the right and they are completely in the wrong. Freedom of the seas needs to be protected, and if they try something they'll get their asses handed to them like in Operation Praying Mantis in 1988. I hope nothing happens since it would almost certainly explode into a bigger war, but a provocation like that can't go unanswered.