BuddyPress.org

If you don’t want anyone in any group to be able to send invites, put the following in your bp-custom.php file:

function bbg_no_send_invites( $can_send_invites ) {
$can_send_invites = false;

return $can_send_invites;
}
add_filter( 'bp_groups_user_can_send_invites', 'bbg_no_send_invites' );

If you want to be more selective than that – for instance, allowing only group admins to invite, or blocking invites only in private groups – you’ll need to put some more logic in there before setting $can_send_invites to false.