Seizing contraband is not an act of war against the nation whose ships are seized; blockading a port is an act of war; what right therefore had Great Britain to adopt measures against Holland, Denmark, and Sweden which virtually amounted to a blockade?
This is the reason why Great Britain, in the pronouncement of March 1, 1915, and the Order in Council of March 11, 1915, did not describe these measures as a "blockade." President Wilson described his attack on Mexico in 1914 as "measures short of war," and now someone referred to the British restrictions on neutral commerce as "measures short of blockade." The British sought another escape from their predicament by justifying this proceeding, not on the general principles of warfare, but on the ground of reprisal.

Germany declared her submarine warfare on merchant ships on February 4, 1915; Great Britain replied with her announcement of March 1st, in which she declared her intention of preventing "commodities of any kind from reaching or leaving Germany." The British advanced this procedure as a retaliation for the illegal warfare which Germany had declared on merchant shipping, both that of the enemy and of neutrals.

"The British and French governments will therefore hold themselves free to detain and take into port ships carrying goods of presumed enemy destination, ownership, and origin." This sentence accurately describes the purposes of a blockade--to cut the enemy off from all commercial relations with the outside world; yet the procedure Great Britain now proposed to follow was not that of a blockade.

When this interdict is classically laid, any ship that attempts to run the lines is penalized with confiscation, along with its cargo; but such a penalty was not to be exacted in the present instance.
Great Britain now proposed to purchase cargoes of conditional contraband discovered on seized ships and return the ships themselves to their owners, and this soon became the established practice.

Not only did the Foreign Office purchase all cotton which was seized on its way to Germany, but it took measures to maintain the price in the markets of the world.