Contrary to media reports, these protections offer a possibility, however slender, that the local judiciary — whose members were largely trained under the British system and have shown admirable independence — might protect him. It’s not clear if any crimes Mr. Snowden might have committed would have been crimes under Hong Kong law — a prerequisite for extradition. The United States might also have to promise not to impose capital punishment on Mr. Snowden — which could be a major sticking point. Finally, our judges would have to make sure that any removal proceedings would be consistent with the International Covenant on Civil and Political Rights, which our judges (unlike their American counterparts) take seriously.

All that said, Beijing holds the cards. In 2004, a Libyan dissident, Sami al-Saadi, and his family were reportedly detained by the Hong Kong authorities and forced back to Libya, without due process of law. Mr. Saadi complained that American and British intelligence officers took part in his forcible repatriation. He was subsequently subjected to torture and inhumane treatment. He has sued both the British and Hong Kong governments.

Our judiciary, however vital, has its limits. The Hong Kong Court of Final Appeal is our highest court. But if a court case is understood to involve the Basic Law — the quasi-constitution of Hong Kong — the court can request from the Standing Committee of the National People’s Congress, a political organ in Beijing, a reinterpretation of the Basic Law. China may also initiate its own request for interpretation — bypassing the judiciary entirely, though such pre-emptive action, in this case, could be bad for Beijing’s image, as it could be seen as caving in to American demands, especially so soon after last week’s summit meeting between President Obama and China’s president, Xi Jinping.