A more thorough explanation:

Term: liquere
Definition: In Roman law, liquere means to be clear, evident, or apparent. If a judex (a judge) appointed to try a civil case swears under oath sibi non liquere ("that it was not clear to him"), he would be discharged from deciding the case. This means that if the judge doesn't understand the case or if the evidence is not clear, he cannot make a decision.
Example: If a judge is presented with a case where the evidence is not clear, he might say "sibi non liquere" and refuse to make a decision. For example, if a person is accused of stealing something but there is no clear evidence that they did it, the judge might say "sibi non liquere" and the case would be dismissed.