shall not allow forest products to be laden aboard a vessel clearing for a foreign port until the shipper shall produce a receipt from an internal-revenue official showing that the forest ch arges upon such products have been paid or a certificate from a proper official of the Bureau of Forestry showing that the products were taken from private lands properly registered in the Bureau of Forestry. [165-1, 2.] SECTION  1395 . Lading of Fibrous Products . — A collector of customs shall not permit abacá, maguey, or sisal or other fibrous products for which standard grades have been established by the Director of Agriculture to be laden aboard a vessel clearing for a f oreign port, unless the shipment conforms to the requirements of law relative to the shipment of such fibers. SECTION  1396 . Detention of Warlike Vessel Containing Arms and Munitions . — Collectors shall detain any vessel of commercial register manifestly built for warlike purposes and about to depart from the Philippine Islands with a cargo consisting principally of  arms and munitions of war when the number of men shipped on board or other circumstances render it probable that such vessel is intended to be employed by the owner or owners to cruise or commit hostilities upon the subjects, citizens, or property of any f oreign prince or state, or of any colony, district, or people with whom the United States are at peace, until the decision of the Governor-General of the Islands be had thereon, or until the owner or owners shall give bond or security, in double the valu e of the vessel and cargo, that she will not be so employed, if in the discretion of the collector of customs such bond will prevent the violation of the provisions of this section. [355-114.] Importation of Merchandise in General  SECTION  1397 . Merchandise to be Imported Only Through Customhouse . — All merchandise introduced into the Philippine Islands, whether subject to duty or not, shall be entered through a customhouse at a port of entry. [355-397.] SECTION  1398 . Special Surveillance for Protection of Customs and Prevention of Smuggling . — In order to prevent smuggling and to secure the collection of the legal duties the customs service shall exercise surveillance over the coast, beginning when a vess el enters Philippine waters and concluding when the merchandise imported therein has been legally passed through the Copyright 2012 CD Technologies Asia, Inc. and Accesslaw, Inc. Philippine Law Encyclopedia 2011 410 ARTICLE  VII