First, such a company cannot be registered in the industrial and commercial bureau. If you register other types of companies and then carry out detective business, it will inevitably lead to exceeding the scope of business. Commercial contracts formed by out-of-scope operations are not necessarily invalid. Operating beyond the scope is not necessarily subject to legal sanctions. Not in the definition of legal and illegal.
Second, citizens have no right to be detectives. Conducting detective business may be suspected of infringing on the legitimate rights and interests of others, such as privacy. If there is an act that infringes on the legitimate rights and interests of others, it may be suspected of violating the law and should be punished by law. The detective entrustment business signed in this matter may be deemed invalid. At this time, it can be considered illegal and even suspected of illegal business.
Third, the detective business may not necessarily step on the legal red line. For example, assisting the parties to catch rape is a legal sideline, or it belongs to an area that the government does not control. There is no point in discussing whether it is legal or not.
So generally speaking, it is illegal to carry out detective business.