The United States and Hong Kong signed an extradition treaty which came into effect in 1998, a year after Hong Kong returned from British to Chinese rule. Scores of Americans have been sent back home for trial since then.

While espionage and theft of state secrets are not cited specifically in the treaty, equivalent charges could be pressed against Snowden under Hong Kong’s Official Secrets Ordinance, legal experts said.

If Hong Kong authorities did not charge Snowden with an equivalent crime, authorities could not extradite him, lawyers said. In the absence of charges, Snowden was also theoretically free to leave the city, one legal expert said.

Simon Young, a law professor at the University of Hong Kong, said that while the first charge involving theft might readily find equivalence in Hong Kong, the latter two spying offences will likely attract “litigation and dispute” in the courts.