The pilots in each category of pilots licensed by the commissioners shall maintain a regular system of rotation in the assignment to vessels of the pilots in their category, and any pilot who shall fail to accept an assignment in accordance with such system and shall be subject to a fine not exceeding $50 and a suspension of his license for not more than 30 days and, in the event that the circumstances attending such failure shall involve intoxication or wilful refusal to accept duty, such pilot shall be tried for such offense or offenses.