Seventeen convicted drug traffickers should be freed because a treaty with Thailand expired at the handover, a court heard yesterday. Hong Kong citizens convicted in Thailand are being held illegally because the accord allowing them to serve their terms here ran out on July 1 last year, judges were told. 'They are undoubtedly bad men,' their barrister, Phillip Dykes SC, told the Court of Appeal. But he said they nevertheless had to be freed. Negotiations for a similar arrangement with Thailand and the post-handover Government have yet to be formalised. 'If no new arrangement was brought into force, detention is unlawful,' Mr Dykes argued. The 17 convicts, whose cases were all separate, were transferred to Hong Kong in the early 1990s. The Thai courts had dealt them sentences averaging 40 years for crimes involving less than a kilogram of heroin each. If they had been convicted and sentenced in Hong Kong, most of them would already have been freed. The case continues before Mr Justice Gerald Nazareth, Mr Justice Simon Mayo and Mr Justice Benjamin Liu Tsz-ming.