Hong Kong does not have a rendition agreement with the mainland. The Cheung case prompted calls for one to be put in place. Negotiations between Hong Kong and the central government began in 1998. The aim was to complete them by 2000.

It has not explained why 20 years of talks failed to seal a rendition deal, yet transfers to the mainland on a case-by-case basis are now considered possible. Details of the long negotiations have been kept secret. This would be a good time to make them public, to inform the ongoing debate.

The Cheung case raised concerns about Hong Kong people arrested on the mainland for offences committed in the city. On which side of the border should they be tried? It is uncertain which courts should have priority in such cases. Any rendition agreement should resolve this by establishing clear rules. But it forms no part of the current proposal.

What about mainland residents? Would they be sent to Hong Kong for trial if accused of crimes in the city? That appears to be in doubt and needs to be clarified.

Even then, concerns would remain. At the heart of the problem is the lack of fair trial guarantees under the mainland system. The government’s proposal includes some safeguards. Suspects would not be returned to face the death penalty and would only be transferred for certain crimes which also exist in Hong Kong. There would be no transfer for political crimes. But these are not sufficient to ensure that suspects would be fairly tried on the mainland.

At the time of the Cheung case, various solutions were put forward. One idea was to incorporate fair trial standards in the city’s Bill of Rights in a rendition agreement. Another was that suspects could be tried in Hong Kong courts for crimes committed on the mainland. Maybe Hong Kong people jailed on the mainland could be returned to the city to serve their sentence. Perhaps, it was said, an agency could be set up to monitor the mainland trials.

Some of these ideas, or similar ones, have been put forward again in response to the government’s proposal, notably by the legal profession. All of these suggestions deserve thorough consideration.

The government stresses that the city’s courts would need to approve any transfer. But the role of the courts in such proceedings is usually limited. And they may find it difficult to inquire into the legitimacy of cases from the mainland, especially if they concern matters of political sensitivity.

Ultimately, the decision on whether to transfer will lie with the chief executive. For sovereign states, this is an important safeguard, because the government can always decide not to transfer one of its own citizens. But the chief executive is in a different position. He or she is appointed by Beijing and constitutionally accountable to the central government. It would be difficult for any chief executive to resist demands from Beijing for a suspect to be transferred.

The government should not seek to quickly push this legislation through. There is a need for careful consideration and wide consultation. The issues are complex and the potential consequences for Hong Kong serious.

Cheung, the gangster, might not be regarded as the best example of the need for such an agreement. Some might say the Hong Kong system let him slip through the net and the mainland one dealt with him efficiently. But that misses the point. Under Hong Kong’s system, everyone is equal before the law and no one is considered guilty until fairly proven to be so. That should apply whether a suspect is tried in Hong Kong or sent to the mainland.

Cliff Buddle is the Post’s editor of special projects