Eadem est ratio, eadem est lex is a legal maxim in Latin. The maxim states ‘the same reason, the same law.’ The principle simply states that if the reason is same, the law is the same.
The following is an example of a case law referring to the maxim:
If one compares the societal and individual interests involved in cases of minors seeking abortions with cases where parental rights may be terminated due to a parent's prolonged mental illness or mental deficiency, it seems that the function and necessity of a guardian ad litem in these cases is analogous, if not identical. Therefore, eadem est ratio, eadem est lex (the reason being the same, the law is the same). In both cases the duties of a guardian [**726] ad litem are not coextensive with those of legal counsel.