Well, I don't see how you can have a siege if you CAN'T starve them out! It is a normal part of war.The 1906 Hague conventions, now known as the Geneva conventions, made it a war crime to do any economic sanctions on civilian commerce.
The original goal was to prevent starvation siege of walled cities.
But the principle is universal and still applies.
Hindering civilian commerce is and always has been illegal.
The fact we starved out the Germans and the Japanese, does not make it any more legal.
It is still a war crime and immoral.
I could search the Geneva conventions again and find the quotes, but I should not have to.
It should be obvious that blocking civilian commerce always inherently has to be a war crime.
Though I THINK the only walled city vulnerable to siege left is Gaza. And nobody much cares about them anymore.