A more thorough explanation:

Definition: According to his interest; to the extent of his interest.

Example: A third party may be allowed to intervene in a legal case pro interesse suo, meaning they have a personal interest in the outcome of the case.

Explanation: Pro interesse suo is a Latin term used in legal contexts to refer to someone acting in their own personal interest. In the example given, the third party has a personal stake in the outcome of the case, and therefore has a right to intervene. This term is often used in situations where someone's personal interests may conflict with the interests of others involved in a legal matter.