A more thorough explanation:

Definition: Mero motu is a Latin term that means "on his mere motion." It refers to doing something voluntarily, without any suggestion or influence from another person. In the past, it was sometimes used in reference to a court, as an equivalent of "sua sponte" or "on its own motion."

• He resigned from his job mero motu, without any pressure from his boss or colleagues.
• The judge dismissed the case ex mero motu, meaning that he did it on his own initiative, without any request from the parties involved.

These examples illustrate how mero motu is used to describe actions that are taken voluntarily, without any external influence or persuasion. In the first example, the person resigned from their job of their own accord, without any pressure from others. In the second example, the judge dismissed the case on his own initiative, without any request from the parties involved.