Here this would make it more secure so that only current channel ops can add access. You also don't need the if (%access == on) more than once.

on @*:TEXT:!access*:#: {
  if (%access == on) {
    if ($2 == add) { 
      cs access $chan add $3 $4
      notice $chan $3 Is added to Level $4
    }
    elseif ($2 == del) { 
      cs access $chan del $3
      notice $chan $3 Deleted from Access list
    }
    elseif ($2 == list) { 
      cs access $chan list 
      set %anick $nick
    }
    else { halt }
  }
}