This is not one of the more common interview questions that you may encounter but it is one that you should be prepared to answer. The purpose of this type of interview question is to find out more information about your ethics as well as how you would handle a situation you did not agree with. This is important as this is the type of situation that you could very easily encounter in the workplace so you should be fully prepared to effectively answer this question.
If you have experienced this type of situation in the past in a prior job then you will be better prepared to develop an answer to this question. On the other hand, if you have not experienced this type of situation then you would need to formulate your answer based on how you think you would react if you were asked to work under a policy that you did not agree with.
There are different ways in which this type of situation can be handled. One way would be to say that you would not work under a policy that you disagreed with. There are certainly many employees that would take this approach if they were faced with a situation where they needed to work with a policy they did not condone. The problem with this type of answer is that it shows that you may not be flexible and could be difficult to work with. Instead of taking this type of approach you might instead talk about a situation in which you sought to learn more about the policy so that you could understand it better. You might still disagree with the policy, but at least you would understand more about it which may help you to feel better about the situation. Your answer might also be based upon the specific situation. For example, if the policy in question was something that was truly unethical then it very well might be something that you could not continue to work under.
In answering this question you need to make sure that you are completely honest but you also need to demonstrate that you are able to be flexible when working in a situation that you do not entirely agree with as compromise is an important part of the workplace.