Being unethical is a moral judgement.
What is unethical may be different according to different individuals and may vary with difference in culture and time.
It may well be unethical to disclose the private lives of TV stars but such acts may not be actionable legally.
Is it necessary, or is it possible, to set standards to judge what act be considered unethical? And by what authorities should these standards be set?

When we were students, ethical issues were taught to be measured against the "ABCDE" rules: automomy, beneficial, confidentiality, do not harm, and equity.

Doctors, because of the sensitive nature of their profession, tend to be bounded by ethical judgements. The earliest set of rules was found in the Hippocratic oath, which was formaly sworn by every doctor upon qualification, and is still of practical relevance to the medical profession.

Doctors in Hong Kong need to understand ethics. And many of us would like to know exactly how "unethical" should be defined. This is because "unethical" has been linked with "professional misconduct", which would result in diciplinary actions according to section 21(1)(b) of the Medical Registration Ordinance, Cap 161.
The Professional Code and Conduct states that:
" The definition of 'misconduct in a professional respect' can be broadly defined as 'If a medical practitioner in the pursuit of his/her profession has done something which will be reasonably regarded as disgraceful, unethical or dishonourable by his/her professional colleagues of good repute and competency, then it is open to the Medical Council of Hong Kong, if that be shown, to say that he/she has been guilty of professional misconduct'.
The seriousness of misconduct will be judged by the rules, be they written or unwritten, of the profession itself."

One logical approach in the interpretation of this piece of statute is that "professional misconduct" is:
1. performance of something disgraceful, unethical or dishonourable
2. in the pursuit of a medical practitioner's profession
3. as reasonably regarded by his professional colleagues of good repute and competency
4. as open to the decision o fthe Medical Council of Hong Kong

So it is essential to establish both 1. and 2. to prove professional misconduct, and the standard of what constitues "disgraceful, unethical or dishonorable" acts to be measured by 3.
A doctor who committed theft and attempting to obtain property by deception was regarded not to be professional misconduct because the act was not in the pursuit of a medical practitioner's profession. (Dr. Kwan Chee Keung v. the MCHK CACV000265/1997)

However, a different approach was adopted by the Medical Council and the courts.
The phrase "misconduct in any professional respect" to be found in section 21(1)(b) of Cap. 161 was considered by the Court of Appeal in Koo Kwok Ho v The Medical Council of Hong Kong, (unreported), Civil Appeal No. 23 of 1988. In that case, the court adopted the approach of the Judicial Committee in Doughty v General Dental Council [1987] 3 WLR 769.
The test for "msiconduct in any professional respect" given was simply:
"whether the doctor's conduct has fallen short of the standard expected amongst doctors."

This test had been challenged and tested by defence counsels in Dr Cheung Sau Yi v The Medical Council of Hong Kong [1998] 2 HKLRD 890 and Dr. To Chun Fung v. The Medical Council of Hong Kong CACV 206/2000.

In the latter case, Leading counsel for the appellant no longer challenged the correctness of the decision in Koo's case . Instead, Mr Huggins SC submitted that "the true legal position is that although as a matter of law misconduct does have to be connected with the profession and has to fall short of the standard expected amongst doctors, it is still for the Council to determine what sort and degree of falling short will be regarded as worthy of condemnation and punishment by the Council, and the Council has, as a matter of policy, determined and pronounced that such conduct must have the ingredients of being 'disgraceful, unethical or dishonourable.' This, Mr Huggins labelled as 'the litmus test'."
This "litmus test" was somewhat similar to the straightforward interpretation of the statute as mentioned above.

However, Hon Le Pichon JA pointed out in the judgement of Dr. To Chun Fung that: "It is to be noted that in the post-Koo editions of the Code, "misconduct" is no longer equated with "infamous conduct". Nor does the Code seeks to define "misconduct" by reference to the litmus test. All it sought to do was to "broadly define" misconduct. The 'definition' proffered was not meant to be exhaustive. That is apparent from the Introduction to Part I of the Code where it is specifically stated that the Code: 'is only a guide and is by no means exhaustive ... It is not a legal document.'"

He then went on in his judgement: "the correct test for "misconduct in a professional respect" is that laid out in Koo's case. There is misconduct within section 21(1)(b) if it can be established that there has been a 'falling short of standards'. As Cons VP observed, "[t]he best judges of that are the doctors themselves" since "what was expected of a doctor in the given circumstances was something which the doctors of the Council would know from their own professional experience." There is no room for the application of the litmus test with its overtones of moral stigma or turpitude. "

So there seems to be no room for the consideration of the "disgraceful, unethical or dishonourable" part and the single test for professional misconduct is now a "falling short of standard"; though one might consider another somewhat circular arguement:
that the standard is set with consideration of and reference to whether the action is "disgraceful, unethical or dishonourable".