Its World Guard, and you have to set it as the rank only entrance.
Example:
/rg flag <region_ID> entry deny
/rg flag <region_ID> entry -g nonmembers
Deny entry to anyone who is not a member (or owner).
/rg flag <region_ID> exit deny
/rg flag <region_ID> exit -g nonowners
Deny exit to anyone who is not an owner.
/rg addmember <region_ID> g:Builder
/rg addowner <region_ID> g:VIP
Add the "Builder" group to members and the "VIP" group to owners.
Thus, only Builders and VIPs would be able to enter, and only VIPs would be able to exit. All other groups would be denied entry
