A more thorough explanation:

de licentia transfretandi

De licentia transfretandi is a historical legal term that means "permission to cross the sea." It refers to a writ that was issued to the wardens of seaports, instructing them to allow a specific person to cross the sea under certain conditions.

An example of de licentia transfretandi would be a writ issued to a merchant who needed to travel to another country to conduct business. The writ would specify the conditions under which the merchant was allowed to cross the sea, such as the purpose of the trip and the length of time they were allowed to stay.

Another example would be a writ issued to a diplomat who needed to travel to another country to negotiate a treaty. The writ would specify the conditions under which the diplomat was allowed to cross the sea, such as the purpose of the trip and the terms of the treaty they were negotiating.

These examples illustrate how de licentia transfretandi was used to regulate travel across the sea in historical times, ensuring that only those who had permission and met certain conditions were allowed to make the journey.