If yes, and they're good with it, then go for it.
If yes and they're not good with it, then there's your answer.
If no, then you have to ask yourself why it is that you feel the need to not disclose this. From an ethical standpoint, the fact that you are not telling them indicates that you recognize there is at least a potential moral dilemma. Citing company policy does not absolve you from the underlying ethical considerations.