A procedure is owned by the user who created it and that user can execute it without permission.
Permission to execute the procedure can be granted to other users using the GRANT EXECUTE command. For example, the owner of the procedure new_dept allows another_user to execute new_dept with the statement:
GRANT EXECUTE ON new_dept TO another_user
The following statement revokes permission to execute the procedure:
REVOKE EXECUTE ON new_dept FROM another_user
See System Administration Guide: Volume 1 > Managing User IDs and Permissions > Managing Individual User IDs and Permissions > Granting Permissions on Procedures in Interactive SQL.