A U.S. citizen may acquire foreign citizenship by marriage, or a person naturalized as a U.S. citizen may not lose the citizenship of the country of birth. U.S. law does not mention dual nationality or require a person to choose one citizenship or another. Also, a person who is automatically granted another citizenship does not risk losing U.S. citizenship. However, a person who acquires a foreign citizenship by applying for it may lose U.S. citizenship. In order to lose U.S. citizenship, the law requires that the person must apply for the foreign citizenship voluntarily, by free choice, and with the intention to give up U.S. citizenship.
http://travel.state.gov/travel/cis_pa_tw/cis/cis_1753.html
Perhaps, you could provide a link to the law that states that a person gives up his status as a natural born citizen if he for any point in his life is considered a dual citizen.
“citizenship by marriage”
Would it help with your understanding of Perkins v Elg if this is pointed out?
That is an example of court usurpation of what should be legislation. It is for the court to decide. See my immediate prior post, about why it is absurd to apply this in the instance of the question of whether or not one is a "natural born Citizen."
The language "natural born Citizen" was at its essence used to refer to someone without any other allegiance or jurisdicion.
See the John Jay letter here, which spells this out, in the common understanding maintained at the time, as per Vatel and Tucker.
Afroyim v. Rusk and its subsequent judicial activist decisions (and legislatively derelict abdications of responsibility) do not touch "natural born Citizen," even if they are allowed to continue to wrongly pollute court decisions.
Here is the John Jay letter.
http://investigatingobama.blogspot.com/2008/12/wrotnowski-v-bysiewicz-natural-born.html
Here is an explanation of it.
http://investigatingobama.blogspot.com/2008/12/donofrio-dual-citizenship-natural-born.html