Here is my opinion about question. Hope it will helpful to you.
1. Integrity is mainly involved because the key words is "illegal activities". You may conceal or acquiesce their illegal activities, so that you are no longer honest or reliable.
2. From the aspect of objectivity, there is more concerns on if you may act like-minded or you will follow the client's decision under some close relationships or situations that involving common interests.
3. Professional behaviour is the most tricky one. This principle requires you being a professional accountant must comply with relevant laws and regulations.You are the object of compliance and then you can act in a professional way, but that doesn't mean you should make your clients
to abide by the laws and regulations.
Kind regards,
Yuan Liang