Res ipsa loquitur - "The thing speaks for itself." Used in tort law when there is no proof of what caused the harm, but it is most likely only the thing that could have caused the harm.⏎
Salus populi suprema lex esto - "The good of the people shall be the supreme law." Used variously as a motto, a reminder, or a notion of how the law and governments in general should be.⏎
Solve et repete - Respect your obligation first, then you can ask for reimbursement. Used in those situations in which one of the two (or more) parties needs to complete his obligation before being allowed to ask for the opposite obligation to be respected by his counter party. Usually this principle is used in fields and subjects in which a certain general steadiness or uniformity of the system has been considered a relevant value by the legislator. The case is typical of service contracts with repeated obligations (like with gas, water, electricity providers and similars), in which irregularities on one side cannot be balanced if not in a regular situation (i.e., of payments) on the other side. The customer, for example, might be asked to pay regularly the new bill, before contesting the previous one in which he found irregular calculations, and asking for a balancement with newer bills; he thus cannot by himself determine a discount in the next payment.⏎