A highly decorated Arab-American sergeant in the US army, who is currently serving as a paratrooper in Afghanistan, faces deportation on his return to the United States because of an irregularity in his immigration papers.

Sgt Hicham Benkabbou has been served with an order to stand trial for deportation as soon as he arrives home, despite the fact that he has been on active service in Afghanistan for almost two years with the 508th parachute infantry regiment, known as the Red Devils.

His lawyers say his treatment illustrates the harsh justice meted out to Arab-Americans by the US immigration authorities.

Benkabbou came to the US from his native Morocco in 1987, and was granted permanent residency four years ago. But when he applied to become a naturalised US citizen in 2005 - by which time he was already serving in the army - immigration officials discovered that he had failed to register his first marriage and alleged that the ceremony had been arranged fraudulently to get him into the country.

Benkabbou says that the marriage was annulled and argues it is therefore irrelevant to his immigration status. "I do not think I deserve to get deported after serving honourably during a time of war!" he wrote in an email from Afghanistan.

"I can read, write and speak Arabic, French and English. I have earned the respect and confidence of my superiors and I shall be a great asset for our country if given the opportunity to become a US citizen."

His case has been taken up by the Association of Patriotic Arab Americans in the Military, which represents up to 3,500 Arab-Americans serving in the armed forces. The anti-discrimination committee for Arab-Americans, ADC, has also protested.

"This is a very disturbing case. This man has been serving our nation, putting his life on the line on behalf of America. This is a setback to attempts to encourage recruitment to the military," said the ADC's Imad Hamad.

The aggressive prosecution of the case has surprised immigration lawyers who point to a directive that advises officials against pressing to deport acting military personnel unless they have been involved in drug trafficking, crimes against children or violence, or unless they pose a danger to the public.

Benkabbou's irregularity over his marriage falls into no such categories.

His lawyer in Atlanta, Georgia, Paul Ford, said the only explanation he could find was that his client was a Muslim, "which sets off all the buzzers. There is no question that Arab-Americans are given a totally different treatment."

Ford said that Benkabbou had been accused of being a terrorist by officials from the immigration enforcement agency, ICE. "In court, ICE lawyers called Morocco a terrorist country, which I found astonishing."

A spokesman for the US citizenship and immigration services said that under privacy laws the department could not discuss individual cases. But he added that in general, "if someone is placed in deportation proceedings, that is not the end of the process. If the case involves someone serving in the military we will look at it very closely.

"We understand the service of those who put themselves in harm's way to preserve the rights in this country that they do not themselves yet enjoy."

Several commanding officers have offered support to Benkabbou. Lieutenant Colonel Peterman said: "It is not an understatement to say that Sgt Benkabbou has been instrumental in sustaining the 508th Parachute Infantry Regiment during this combat deployment to Afghanistan. He is a leader, a problem solver, and possesses the physical gifts of a US paratrooper."