Good question. Abstract below from >>>this link<<<I have wondered for years why we don't blockade or screen traffic into Yemen more often to stem the tide of weapons into the country.
"The law of Blockade is derived from customary law that developed during the height of eighteenth and nineteenth century naval warfare. As a method of warfare that has the goal of crippling an adversary’s economy, blockade can devastate not only the military apparatus of a country, but the civilian population as well. In this manner, it is a method of warfare that cannot distinguish in its effects between civilians and military objectives.
The existing IHL framework governing blockade does not provide satisfactory protections to the civilian populations of affected states. Starvation, malnutrition and disease are the consequential effects of a lengthy and effective blockade.
A new approach to the law of blockade is required, one that will codify contemporary practice and obligate those engaging in blockade operations to ensure that humanitarian relief cannot be denied to affected civilian populations."