§  1001.  Necessary  joinder  of  parties.  (a)  Parties who should be
  joined. Persons who ought to be parties if  complete  relief  is  to  be
  accorded  between the persons who are parties to the action or who might
  be inequitably affected by a  judgment  in  the  action  shall  be  made
  plaintiffs  or  defendants. When a person who should join as a plaintiff
  refuses to do so he may be made a defendant.
    (b) When joinder excused. When a person who  should  be  joined  under
  subdivision    (a) has  not  been  made  a  party  and is subject to the
  jurisdiction of the court,  the  court  shall  order  him  summoned.  If
  jurisdiction over him can be obtained only by his consent or appearance,
  the  court,  when  justice  requires,  may  allow  the action to proceed
  without his being made a party. In  determining  whether  to  allow  the
  action to proceed, the court shall consider:
    1.  whether  the  plaintiff  has  another effective remedy in case the
  action is dismissed on account of the nonjoinder;
    2. the prejudice which may accrue from the nonjoinder to the defendant
  or to the person not joined;
    3. whether and by whom prejudice might have been avoided or may in the
  future be avoided;
    4. the feasibility of a protective provision by order of the court  or
  in the judgment; and
    5. whether an effective judgment may be rendered in the absence of the
  person who is not joined.