What does the sanction mean?
First, I do not think U.N. will approve such sanction since China and Russia for sure will be against it.
Second, even if Europe and U.S. do not buy oil from Iran due to the sanction, you still have other countries that will buy it no matter the sanction by U.S. and Europe. For example, China will still buy from Iran.
Why does Iran need shut down the strait? As long as there are buyers, what does Iran need to worry about?
First, I do not think U.N. will approve such sanction since China and Russia for sure will be against it.
Second, even if Europe and U.S. do not buy oil from Iran due to the sanction, you still have other countries that will buy it no matter the sanction by U.S. and Europe. For example, China will still buy from Iran.
Why does Iran need shut down the strait? As long as there are buyers, what does Iran need to worry about?