Definition: The "three year rule" applies to individuals who have reached the age of consent, but have not reached the age of majority. It is not a regulation in all locales.
The "three year rule" means that a minor who has reached the age of consent cannot legally consent to having sex with someone who is three years older.
Also Known As: The Four Year Rule, and the Five Year Rule
Examples:
For instance, a 17 year old could only legally consent to sexual activity with someone who is between the ages of 17 and 20 years old.

