"Sufficient justification" means having enough valid reasons or evidence to support or prove something. It implies that the explanation or argument is convincing enough to justify or support a particular action, decision, or belief. Full definition
The mere existence of a group is not sufficient justification for continuation of funding. (sciencemag.org)
In most other contexts, we would say such a burden is not sufficient justification. (firstthings.com)
To be denied that right by one parent, without sufficient justification such as abuse, is itself a form of child abuse. (illinoisdivorcelawyerblog.com)