The father of an Alabama woman who joined ISIS years ago is suing the Trump administration in an effort to bring her back home to the U.S. Earlier this week, Secretary of State Mike Pompeo declared that Hoda Muthana was  not a U.S. citizen  and therefore not allowed back in the country.

Her father's  lawsuit claims  that the Trump administration's move is "unconstitutionally robbing [Muthana and her 18-month-old son] of their rights as United States citizens." Muthana's family claims she was born in New Jersey.

But the question about her citizenship at least partly revolves around the timing of her father's employment as a Yemeni diplomat.

Now, in most cases, children born in the U.S. are automatically granted citizenship.

But children of accredited foreign diplomatic officers are an exception under the  Immigration and Nationality Act , since they aren't subject to U.S. law.

Pompeo  told NBC News  that her father's diplomatic status at the time of her birth means Muthana was never a U.S. citizen.

But Muthana's father claims he stopped working as a diplomat months before she was born.  In a letter obtained by CNN, Muthana wrote that she was angry and arrogant when she left the U.S. to go to Syria five years ago, and that witnessing war conditions and the deaths of two of her husbands has changed her mind.

The lawsuit says officials  first determined  that Muthana was not a U.S. citizen in 2016 when President Barack Obama was in office.

Her passport was revoked at that time.

Additional reporting from  Newsy affiliate CNN .