The Guano Islands Act

In our understanding of Space Law, I thought it would be good for this new article to focus on the U.S. Guano Islands Act. The Guano Islands Act, a United States federal law passed by the U.S. Congress (the bicameral legislature of the federal government of the United States of America, consisting of two chambers: the House of Representatives and the Senate) in 1856, enables citizens of the United States of America to take possession, in the name of the United States of America, of unclaimed islands containing guano (the accumulated excrement of seabirds and bats) deposits. Basically, any American who discovers large deposits of bird excrement on an island can legally claim that island as U.S. territory.

The islands can be located anywhere, so long as they are not occupied and not within the jurisdiction of another government. It also empowers the President of the United States of America to use the military to protect such interests and establishes the criminal jurisdiction of the United States of America in these territories. The Act from the nineteenth century continues to be part of the law of the United States of America. The most recent Guano Islands Act claim was made to Navassa Island (a small uninhabited island in the Caribbean Sea); however, the claim was discarded because an American court ruled the island was already under American jurisdiction. We thought that, regarding the debates going on around the lawfulness of space mining activities, it would be good to have a look at this Act.


In the 1840s, guano came to be prised as a source of saltpetre for gunpowder, as well as an agricultural fertiliser. The United States of America began importing it in 1843. In 1840, the first Peruvian guano was shipped to Europe, arriving in London. Over the next two years, one hundred and eighty-two tons were shipped to England. Just twenty years later, in 1862, that amount had risen to almost half a million tons. The first shipment of guano arrived in the United States of America in 1844, and consisted of seven hundred tons of the stuff. At the outset of the guano boom, Peru more or less had a monopoly on the good, and the American and Peruvian governments weren’t on particularly good terms with each other. Before long, Americans began seeking out alternative sources of bird crap.

In the mid-nineteenth century, explorers headed out to sea, hoping to claim new islands for the United States of America. Soon, the problem arose of what to do if Americans wanted to extract guano from locations already claimed by other governments — in particular uninhabited islands, where birds had been dropping their excrement for millennia with no human interference. The “guano mania” of the 1850s led to high prices in an oligopolistic market, attempts of price control, and fear of resource exhaustion; and so, the Guano Islands Act came to be.

The Guano Islands Act

The Guano Islands Act notably states that “Whenever any citizen of the United States discovers a deposit of guano on any island, rock, or key, not within the lawful jurisdiction of any other government, and not occupied by the citizens of any other government, and takes peaceable possession thereof, and occupies the same, such island, rock, or key may, at the discretion of the President, be considered as appertaining to the United States”.

The U.S. Act then adds that “The discoverer shall, as soon as practicable, give notice verified by affidavit, to the Department of State, of such discovery, occupation, and possession, describing the island, rock, or key, and the latitude and longitude thereof, as near as may be, and showing that such possession was taken in the name of the United States; and shall furnish satisfactory evidence to the State Department that such island, rock, or key was not, at the time of the discovery thereof, or of the taking possession and occupation thereof by the claimants, in the possession or occupation of any other government or of the citizens of any other government, before the same shall be considered as appertaining to the United States”.

The Guano Islands Act declares that “The discoverer, or his assigns, being citizens of the United States, may be allowed, at the pleasure of Congress, the exclusive right of occupying such island, rocks, or keys, for the purpose of obtaining guano, and of selling and delivering the same to citizens of the United States, to be used therein, and may be allowed to charge and receive for every ton thereof delivered alongside a vessel, in proper tubs, within reach of ship’s tackle, a sum not exceeding $8 per ton for the best quality, or $4 for every ton taken while in its native place of deposit”.

Then, “All acts done, and offenses or crimes committed, on any island, rock, or key mentioned in section 1411 of this title, by persons who may land thereon, or in the waters adjacent thereto, shall be deemed committed on the high seas, on board a merchant ship or vessel belonging to the United States; and shall be punished according to the laws of the United States relating to such ships or vessels and offenses on the high seas, which laws for the purpose aforesaid are extended over such islands, rocks, and keys”.

It continues with the following: “The President is authorized, at his discretion, to employ the land and naval forces of the United States to protect the rights of the discoverer or of his widow, heir, executor, administrator, or assigns”. And finally, “Nothing in this chapter contained shall be construed as obliging the United States to retain possession of the islands, rocks, or keys, after the guano shall have been removed from the same”.

More than one hundred islands have been claimed for the United States of America under the Guano Islands Act, but most claims have been withdrawn. The Act specifically allows the islands to be considered possessions of the United States of America. The Act does not specify what the status of the territory is after it is abandoned by private U.S. interests, or the guano is exhausted, creating neither obligation to nor prohibition of retaining possession.