www.usembassy.de/services/dualnationality.htm
.....
4. Under German law, a person may not have more than one citizenship unless
he/she was born with both, as described in paragraphs 2 and 3 above. Thus,
German law requires an American who becomes a German citizen through the
Einbürgerung process (see paragraph 5 in the section entitled, "Basic Primer
on German Citizenship Law") to formally renounce his/her American citizenship,
and a German who becomes an American citizen (see paragraph 5 in the section
entitled, "Basic Primer on American Citizenship Law") to give up his/her
German citizenship.
Alles klar?
Przy okazji, z tego samego zrodla pare obowiazkow wynikajacych z podwojnego
obywatelstwa D-USA:
a. All American-German dual nationals must enter the United States with a
valid U.S. passport; to enter with only a German passport or Kinderausweis is
a violation of U.S. law.
b. Depending on the laws in effect, level of income, source of income, etc.,
an American-German dual national may owe taxes in both countries. All dual
nationals must report all worldwide income by filing an annual U.S. income tax
return, regardless of whether they owe taxes to the U.S. or pay taxes
elsewhere. For more information about taxes, please contact the Internal
Revenue Service, U.S. Embassy, Clayallee 170, 14195 Berlin, 030 8305 1140 or
Fax 030 8305 1145, or your local German tax office.
c. An American-German male dual national must register with the U.S. Selective
Service System within three months of his eighteenth birthday; that he is also
a German citizen does not exempt him from that requirement. Registering with
the Selective Service System, however, has no effect on his German citizenship.
