By filing a criminal complaint, prosecutors have a legal basis to make the request of the authorities in Hong Kong. Prosecutors now have 60 days to file an indictment, probably also under seal, and can then move to have Snowden extradited from Hong Kong for trial in the United States.
Snowden, however, can fight the U.S. effort to have him extradited in the courts in Hong Kong. Any court battle is likely to reach Hong Kong’s highest court, and could last many months, lawyers in the U.S. and Hong Kong said.
The United States has an extradition treaty with Hong Kong, and U.S. officials said cooperation with the Chinese territory, which enjoys some autonomy from Beijing, has been good in previous cases.
The treaty, however, has an exception for political offenses, and espionage has traditionally been treated as a political offense. Snowden’s defense team in Hong Kong is likely to invoke part of the extradition treaty with the United States, which states that suspects will not be turned over to face criminal trial for offenses of a “political character.”
Snowden could also remain in Hong Kong if the Chinese government decides that it is not in the defense or foreign policy interests of the government in Beijing to have him sent back to the United States for trial.
Snowden could also apply for asylum in Hong Kong, or attempt to reach another jurisdiction and seek asylum there before the authorities in Hong Kong act. (source)