Of course, no one has the right to enter the territory of another state, even if they are granted a visa. It is, rather, a privilege; our Immigration Department was and is under no obligation to allow in Wang, Wuer, or anyone else. But any decision to grant or deny entry cannot be taken arbitrarily or in a discriminatory manner. It is also desirable, even if not legally required, to give the individual concerned the reasons for the decision, as well as making the information public if matters of the wider public interest are at stake. The typical Immigration Department response, that it does not comment on individual cases and always makes decisions in view of the relevant law, policy and circumstances, is not very helpful.

To show it is committed to transparency, the administration should issue a white paper clarifying its position, thus helping to dispel legitimate concerns that decisions are made in accordance with Beijing's wishes.

Given that the chief executive has declined to comment on, or answer questions related to, sensitive issues, society should seek to make Hong Kong's autonomy a central issue of public debate during the next chief executive election. People have a right to know what, if anything, the next leader would do to uphold Hong Kong's autonomy, which is guaranteed by the Basic Law. The chief executive is accountable to the central government only in accordance with, and not in derogation of, the Basic Law provisions.

People living in or visiting Hong Kong are under an obligation to abide by the laws of the city. Article 42 of the Basic Law embodies this general principle. But this does not extend to complying with mainland laws or official policies. Annex III to the Basic Law contains a list of national laws that are applicable in Hong Kong. But, again, it is worth noting that none of these laws directly curtails the discretion of the Hong Kong immigration authorities in considering controls on entry into the city.

Despite claims of ever-increasing globalisation, the 'ideological exclusion' of foreign citizens by states is not unheard of. Nevertheless, authorities should be open about why such decisions are made, rather than hiding behind the wall of national security or public disorder. Secrecy from our officials will only strengthen suspicions that the rule of law and Hong Kong's autonomy are under attack from the invisible hand of the central government.

It is worth recalling that, in 2009, in a case related to a judicial review of a decision to deny entry to Falun Gong members, the Court of Appeal found the Hong Kong government in breach of the duty of candour on several counts - for example, for not providing the court with all relevant evidence. The jury is still out on whether the government has learned any positive lessons from the ruling.

If the government denies entry to people on flimsy grounds, a judicial review remains a possibility. And the courts may strike down the decision if it is found to have been based on irrelevant factors, or if a decision was taken under direction from another authority. But such a course of action is not always easy.

Therefore, democratic accountability as well as civil society activism remain useful tools, and cannot be ignored in such cases. In fact, the extent of Hong Kong's autonomy, like the worth of its human rights, is tested greatly in such difficult times.

We have to constantly guard against encroachment on our freedoms; Hongkongers need to realise this before it's too late. Not only are our freedoms at stake here, but also the future of the SAR and the reliability of international agreements. If the current trends continue, the 'one country, two systems' principle might become 'one country, one system' in many respects well before 2047. I wonder if Szeto Wah would have wanted that.

Surya Deva is an associate professor at the School of Law, City University of Hong Kong