A more thorough explanation:

Term: ad libellum rescribere
Definition: Ad libellum rescribere is a Latin term used in Roman law. It means to write a response to a petition, especially one that is addressed to the emperor. This term is often used in legal contexts.
Examples: A person may write a petition to the emperor asking for a pardon or a reduction in their sentence. The emperor would then respond by ad libellum rescribere, writing a response to the petition. This response could grant the request or deny it. For example, if a person was sentenced to death, they could write a petition to the emperor asking for mercy. The emperor could then respond by ad libellum rescribere, either granting the pardon or upholding the sentence. These examples illustrate how ad libellum rescribere was used in Roman law to address petitions and requests.