War and neutrality — War in general — Effects of outbreak of war — Trading with the enemy — Blocking of Cuban assets by United States Government — Assets in which Cuba or a Cuban national possesses a sufficient interest — Purposes of the Cuban Assets Control Regulations — Whether regulation that Cuba retains sufficient interest in an account in the name of a deceased Cuban national merely because the deceased was a Cuban national is a valid application of the Trading with the Enemy Act — The law of the United States