A former US serviceman arrived at Glasgow International Airport with 160 counterfeit blank French passports.
Fredericks was arrested in January when he arrived from Dubai
Customs officers tracked Gerald Fredericks, 60, from Bangkok through Dubai and into Scotland, where he was arrested by investigators.
He pleaded guilty at Paisley Sheriff Court to furthering "the illegal movement of persons" by being concerned in the supply of fake passports.
Sheriff David Pender sent Fredericks to the High Court for sentencing.
He said: "The maximum I can impose would be five years.
"It may well be that that is deemed sufficient but the High Court should make that decision.
"In these days of international terrorism, the possibility of criminal activity is endless and, on one view, frightening, if these fell into the wrong hands."
Originally from Chicago, Fredericks had been living in Bangkok for eight years where he had been teaching biology.
Depute fiscal John Miller told Paisley Sheriff Court there was an international ring involved.
Fredericks would have received £2,300 on delivery.
Defence agent David Allan said his client had suffered a stroke in 2004 and had got involved in the offence to fund medical bills.
He was said to have been decorated following active service for his country in Vietnam.