Final answer:
Harold, as president of the local tennis club, wields legitimate power or rational-legal authority over the members, as his role legally permits him to enforce club rules and regulations.
Step-by-step explanation:
As the president of a local tennis club, Harold exercises legitimate power over the club's members. This form of power is defined by the German sociologist Max Weber as rational-legal authority, which is legitimized by rules, regulations, and laws. In this case, the club members must adhere to a set number of practice hours and follow a strict uniform code, with the consequence of suspension for noncompliance.
Legitimate power differs from referent power (based on personal admiration or individual charisma), expert power (based on knowledge or expertise), and reward power (based on the ability to provide rewards). Harold's position as club president affirms his authority to enforce the rules and ensures compliance through the established regulations of the club.