Attempting to run a blockade is also an act of war. Declaring a blockade is neither legal nor is it illegal. It is an act of war. Ayalon is exhibiting stating pure propaganda not based in reality when alleging that attempting to run a blockade is a breach of international law. No one country can declare international law; it can only declare war.
Austrian chancellor: Austria and Germany will allow migrants entry (Reuters)
from the article: Israel prepares to intercept French yacht as it sets sail for Gaza