"The judge ordered [Postovoy] to be detained and transported to Washington," Foster said on Thursday.
Magistrate Judge Natalie Adams held earlier a detention hearing at the US District Court for the Middle District of Florida in Tampa.
"Postovoy may appeal the judge’s decision," Foster said.
Foster also said that he did not know when Postovoy is expected to arrive in Washington, where he will be detained or when the next hearing will be.
Postovoy’s family still has to decide who will represent his interests in court.
The US Justice Department said on Wednesday that Postovoy, who lives in Sarasota, Florida, procured and illegally exported microelectronic components with military applications from the United States to Russia through companies he owns or operates in Russia, Hong Kong and elsewhere, without obtaining required licenses.