If an alien goes through the process of obtaining lawful permanent resident status and then becomes a US citizen through the naturalization process, the new citizen is protected from deportation. The only way such a new citizen could be deported is if the government first denaturalized the citizen.
Denaturalization is very rare and the government has to meet a very high burden in order to obtain denaturalization. Almost always, an attempt by the government to denaturalize someone is based upon the government's claim that a new fact has been discovered which, if known at the time of naturalization, would have prevented the alien from ever being naturalized. This usually involves that the person naturalized used a false identity or perpetrated some other kind of fraud on the immigration service.
An attempt to denaturalize someone usually involves litigation brought by the US government in federal court. The Department of Homeland Security takes the position that they can denaturalize someone in an administrative proceeding, but at least one court has held that the regulations which purport to allow DHS to denaturalize someone lack statutory authorization and are therefore void.
If you have questions about denaturalization or if someone is claiming that you or a loved one committed fraud in the immigration context, you should consult with an experienced immigration attorney. Please call us at (314) 961-8200 or visit our contact page.