Feb. 18 (UPI) -- Columbia University graduate student Mohsen Mahdawi had Department of Homeland Security deportation proceedings against him thrown out by an federal immigration judge who ruled DHS had failed to show his removal was legal.

Mahdawi's lawyers filed a letter Tuesday with the U.S. Court of Appeals for the Second Circuit notifying it that the judge in Chelmsford, Mass., had terminated Mahdawi's removal proceedings, the ACLU said in a news release.

Judge Nina Froes' ruling was based on the government's failure to authenticate a memorandum, purportedly from Secretary of State Marco Rubio and which formed the basis for its case for Mahdawi's removal.

Froes questioned whether a photocopy of the document, apparently signed by Rubio, was authentic. The document says Mahdawi's arrest is warranted on grounds his activities in support of Palestinians and protesting the Gaza war "could undermine the Middle East peace process by reinforcing antisemitic sentiment."

However, the ruling was issued without prejudice, meaning the government can challenge the decision before the Board of Immigration Appeals, or file a new case with the same charges, said the ACLU.