Lobby group Family First says it has an independent legal analysis of the child discipline law, which shows it is complex and difficult to apply.
The group asked public law specialists Chen Palmer to look at court cases involving the so-called anti-smacking law since it was passed in 2007.
Family First said the findings include that parents and police struggle to understand and apply section 59 of the Crimes Act.
It said the cases also indicated that even lawyers and judges struggled to apply the law correctly, with examples of cases going to the District Court, the High Court and then being overturned by the Court of Appeal.
Family First said it would get further legal advice on challenging the law.