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Citizenship for those born at sea

Reader Douglas Burnett got to thinking after reading about the question of the impact marrying into one of the tribes had on a woman’s U.S. citizenship last week.

“Your Friday Blog1 got me wondering about ‘what if’ cases,” he wrote.

What if, he wondered:

• “A pregnant woman leaves European port and has child on ship in international waters and first port of call is American? Would the child qualify as American Citizen and qualify for presidency? Does Country of registration for ship make a difference?”

• “Would the same answer for this event hold if this took place on an Aircraft? I realize the soon to be mother would probably not be allowed on an aircraft in that state of pregnancy but what if?”2

Great questions — and, with one twist, having a surprisingly easy answer.

No, a child born under these circumstances to a woman who was not an American citizen would not get American citizenship, not even if the ship or the aircraft was registered here in the United States.


First off, remember that citizenship isn’t directly defined in the Constitution of the United States. The word is used numerous times, but never defined in that document — not even in the amendments.3 The closest we get is in the Fourteenth Amendment which says: “All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.”4

So… what does it mean to be “born … in the United States”?

The first legal authority to weigh in fully on this question was the U.S. Supreme Court in a case involving inheritance of lands in New York when claimed by a man born in pre-Revolutionary War New York. There, the Court stated: “Two things usually concur to create citizenship; first, birth locally within the dominions of the sovereign; and secondly, birth within the protection and obedience, or in other, words, within the ligeance of the sovereign. That is, the party must he born within a place where the sovereign is at the time in full possession and exercise of his power, and the party must also at his birth derive protection from, and consequently owe obedience or allegiance to the sovereign…”5

In the course of the discussion, the Court made this critical comment: “a person who is born on the ocean, is a subject of the prince to whom his parents then owe allegiance; for he is still deemed under the protection of his sovereign, and born in a place where he has dominion in common with all other sovereigns.”6

Now… because this was an aside, not essential to its ruling in that case, the comment was what the law calls dictum: “A remark, statement, or observation of a judge that is not a necessary part of the legal reasoning needed to reach the decision in a case. Although dictum may be cited in a legal argument, it is not binding as legal precedent, meaning that other courts are not required to accept it.”7

But the issue was squarely presented to the U.S. Court of Appeals for the Ninth Circuit in 1928, in the case of a child “born on a merchant vessel of American registry, on the high seas, of parents of the Chinese race and subjects of China, but domiciled in the United States.”8 And there, relying on the language from the earlier Supreme Court case, the court held that a ship on the high seas was not within the territory of the United States for citizenship purposes.

And the rule is the same for births on aircraft.9

And no, it doesn’t matter whether the ship or aircraft is registered in the United States:

• “A U.S.-registered or documented ship on the high seas … is not considered to be part of the United States.”10

• “A U.S.-registered aircraft outside U.S. airspace is not considered to be part of U.S. territory. A child born on such an aircraft outside U.S. airspace does not acquire U.S. citizenship by reason of the place of birth.”11

The twist? Where it gets a little murky is in defining just how close to the United States a ship or aircraft has to be in order for the birth to be considered to have occurred “in the United States.”

The State Department takes the position that “Persons born on ships located within U.S. internal waters . . . are considered to have been born in the United States. … Internal waters include the ports, harbors, bays, and other enclosed areas of the sea along the U.S. coast.”12 The same rule applies to “persons born on planes in airspace above the United States land territory or internal waters.”13 There are specific exceptions like birth on a military ship or aircraft of a foreign nation in government service.

But there’s also something called the territorial sea, defined by law as “the waters, 12 nautical miles wide, adjacent to the coast of the United States and seaward.”14 And there, the State Department says, “there is a substantial legal question whether persons born outside the internal waters of the United States but within the territorial sea are in fact born ‘within the United States’” for citizenship purposes.15

So… for those born on the high seas or in a plane above the high seas, no, they do not become U.S. citizens even if born on a U.S. ship or aircraft.

For those born above the land or the internal waters of the United States, they do have a claim to U.S. citizenship.

And for those born between the internal waters and the 12-mile limit of the territorial sea, well, the State Department says it’ll be decided on a case-by-case basis.

Cite/link to this post: Judy G. Russell, “On the high seas,” The Legal Genealogist ( : posted 15 Feb 2022).


Image courtesy of New York Public Library, CC0 1.0

  1. Judy G. Russell, “A question of citizenship,” The Legal Genealogist, posted 11 Feb 2022 ( : accessed 15 Feb 2022).
  2. Email, “What Citizen am I?,” Douglas Burnett to the author, 12 Feb 2022. By the way, Doug, lots of very pregnant women are allowed on aircraft — and more than one has given birth on a plane. See e.g. Michelle Butterfield, “Woman gives birth to baby on board Delta flight, with help from firefighters, nurse,” Global News, posted 21 Nov 2021 ( : accessed 15 Feb 2022).
  3. See “The U.S. Constitution,” National Constitution Center ( : accessed 15 Feb 2022).
  4. Ibid., Amendment 14.
  5. Inglis v. Trustees of Sailor’s Snug Harbour, 28 U.S. (3 Pet.) 99, 155 (1830).
  6. Ibid.
  7. Wex, Legal Information Institute, Cornell Law School ( : accessed 15 Feb 2022), “dictum.”
  8. Lam Mow v. Nagle, 24 F.2d 316, 317 (9th Cir. 1928).
  9. See “What is Birth in U.S. Airspace?,” 8 FAM 301.1-5, in U.S. Department of State, Foreign Affairs Manual, U.S. Citizenship: Acquisition by Birth in the United States ( : accessed 15 Feb 2022).
  10. Ibid., “Not Included in the Meaning of ‘In the United States,’” 8 FAM 301.1-3a.
  11. Ibid., 8 FAM 301.1-3b.
  12. Ibid., “Birth in U.S. Internal Waters and Territorial Sea,” 8 FAM 301.1-4.
  13. Ibid., “What is Birth in U.S. Airspace?,” 8 FAM 301.1-5.
  14. Territorial sea,” 33 CFR § 2.22.
  15. U.S. Department of State, Foreign Affairs Manual, “Birth in U.S. Internal Waters and Territorial Sea,” 8 FAM 301.1-4.
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