In 1953 Congress placed on the statute books a provision suggestive of the old neutrality acts. Under this law the Secretary of the Treasury, or anyone designated by the President, could seize and detain any carrier-vessel, vehicle or aircraft carrying munitions of war from the United States. The authority to “seize and detain” came into operation whenever an attempt was made to export, ship or take out of the United States any munitions of war or other materials in violation of law. Moreover, the law became operative as long as there was “probable cause to believe” that prohibited items were being removed from the United States in violation of the law.[421] The Merchant Marine Act of 1936 is, of course, another of those organic statutes designed to promote, rehabilitate, and regulate in the interest of the trade and of the public, a segment of the American transportation system. We have already seen that in this Act the government secured the right in time of war emergency to requisition American registered vessels. As a condition of the grant of subsidies toward the construction of vessels in American yards, the Maritime Commission reserved a power of final approval of the design of such vessels. This power was of course shared with the Navy Department which had to approve all defense features in the proposed vessel.[422] Under the terms of the Act any vessels, the construction of which was subsidized, were to be so designed as to be readily and quickly convertible into transport and supply vessels in a time of national emergency.[423] By permitting it to subsidize operation on approved routes, Title VI of the Act in effect enabled the Commission to control also the allocation of American shipping on the various world trade routes. In July 1941 the President was given power, during the emergency which he had declared on May 27 of that year, to authorize the Maritime Commission to issue warrants entitling vessels to priority over merchant vessels not holding such warrants, in the use of facilities for loading, discharging, lighterage or storage of cargoes, the procurement of fuel, towing, overhauling, drydocking or repair of such vessels. Vessels holding warrants had priority among themselves in accordance with the rules of the Maritime Commission.[424] In granting warrants, the Commission was to make fair and reasonable provision for priorities. The criteria for helping the Commission determine priorities were: (1) the importation of substantial quantities of strategic and critical materials, (2) the transportation of substantial quantities of materials when such transportation was requested by any defense agency, and (3) the transportation in the foreign or domestic commerce of the United States of substantial quantities of materials deemed by the Commission to be essential to the defense of the United States.[425]