If you use coercive measures to get people to join your club, it means that you intimidate or force people to make them feel like they have to join.
If you use threats to get what you want from other people, your methods can be described as coercive. It can take nothing more than a strong sense of authority to come across as coercive, or the intimidation can take the form of physical threats. When you're coercive, you're demanding obedience without much concern for what the people you coerce need or want. The Latin root is coercere, which means "to control or restrain."