The facts are not in dispute and are stated . . . as follows: "The plaintiff [Ethel Mackenzie] was born and ever since has resided in the State of California. On August 14, 1909, being then a resident and citizen of this state and of the United States, she was lawfully married to Gordon Mackenzie, a native and subject of the kingdom of Great Britain. . . . On January 22, 1913, she applied to the defendants to be registered as a voter [because California granted women the right to vote]. . . . Registration was refused to her on the ground that, by reason of her marriage to Gordon Mackenzie, a subject of Great Britain, she thereupon took the nationality of her husband and ceased to be a citizen of the United States."

. . . [Mackenzie presented "an earnest argument" that her citizenship derived from] her birth in the United States, and, under the Constitution and laws of the United States, it became a right, privilege, and immunity which could not be taken away from her except as a punishment for crime or by her voluntary expatriation. . . .

The identity of husband and wife is an ancient principle of our jurisprudence [that is, a married couple should be treated as a single legal entity represented by the husband].  . . . [Marriage is] a condition voluntarily entered into, with notice of the consequences. We concur with counsel that citizenship is of tangible worth, and we sympathize with plaintiff in her desire to retain it and in her earnest assertion of it.
But there is involved more than personal considerations. . . . The marriage of an American woman with a foreigner has consequences of like kind, may involve national complications of like kind, as her physical expatriation may involve. Therefore, as long as the relation lasts, it is made tantamount to expatriation.