An exception which confirms the law explains the law.

Explanation

(English-origin maxim.) An exception to a rule confirms the rule's general applicability — the very existence of a stated exception proves that the rule governs all other cases.

Where this applies

• A law says all vehicles must stop at a red light except emergency vehicles with sirens on — the exception for emergency vehicles confirms that the rule applies to everyone else.
• A statute exempts churches from property tax, which confirms that all other property owners must pay — the exception proves the general rule.
• A contract says no refunds except for defective products — the stated exception confirms that in all other cases, the no-refund rule applies.