(a) When Permitted. All persons may join in one action as plaintiffs if they assert a right to relief jointly, severally, or in the alternative in respect to or arising out of the same transaction, occurrence, or series of transactions or occurrences, and if any question of law or fact common to all these persons will arise in the action. All persons may be joined in one action as defendants if there is asserted against them jointly, severally, or in the alternative any right to relief in respect to or arising out of the same transaction, occurrence, or series of transactions or occurrences, and if any question of law or fact common to all defendants will arise in the action. A plaintiff or defendant need not be interested in obtaining or defending against all relief demanded. Judgment may be given for one or more of the plaintiffs according to their respective rights to relief and against one or more defendants according to their respective liabilities.

(b) Safeguards. The court may make such orders as will prevent a party from being embarrassed, delayed, or put to expense by the inclusion of another who asserts no claim against the party and against whom the party asserts no claim, and may order separate trials or make other orders to prevent delay or prejudice.

Source: This Rule is derived as follows:

Section (a) is derived from the 1966 version of Fed. R. Civ. P. 20 (a) and former Rule 313 a, c, d and e.

Section (b) is derived from the 1966 version of Fed. R. Civ. P. 20 (b) and former Rule 501 b.