Maryland Rules of Civil Procedure|Rule 2-214 - Intervention

                                                
(a) Of Right. Upon timely motion, a person shall be permitted to intervene in an action: 
(1) when the person has an unconditional right to intervene as a matter of law; or 
(2) when the person claims an interest relating to the property or transaction that is the subject of the action, and the person is so situated that the disposition of the action may as a practical matter impair or impede the ability to protect that interest unless it is adequately represented by existing parties.
(b) Permissive.
(1)Generally. Upon timely motion a person may be permitted to intervene in an action when the person's claim or defense has a question of law or fact in common with the action.
(2)Governmental Interest. Upon timely motion the federal government, the State, a political subdivision of the State, or any officer or agency of any of them may be permitted to intervene in an action when the validity of a constitutional provision, charter provision, statute, ordinance, regulation, executive order, requirement, or agreement affecting the moving party is drawn in question in the action, or when a party to an action relies for ground of claim or defense on such constitutional provision, charter provision, statute, ordinance, regulation, executive order, requirement, or agreement.
(3)Considerations. In exercising its discretion the court shall consider whether the intervention will unduly delay or prejudice the adjudication of the rights of the original parties.
(c) Procedure. A person desiring to intervene shall file and serve a motion to intervene. The motion shall state the grounds therefor and shall be accompanied by a copy of the proposed pleading, motion, or response setting forth the claim or defense for which intervention is sought. An order granting intervention shall designate the intervenor as a plaintiff or a defendant. Thereupon, the intervenor shall promptly file the pleading, motion, or response and serve it upon all parties.
Md. R. Civ. P. Cir. Ct. 2-214
 This Rule is derived as follows:
Section (a) is derived from the 1966 version of Fed. R. Civ. P. 24(a).
Section (b)
Subsection (b)(1) is derived from former Rule 208 b 1.
Subsection (b)(2) is derived from former Rule 208 b 2.
Subsection (b)(3) is derived from the last sentence of the 1966 version of Fed. R. Civ. P. 24(b).
Section (c) is derived from the 1966 version of Fed. R. Civ. P. 24(c) and former Rule 208 c.
Adopted April 6, 1984, eff. July 1, 1984. Amended Nov. 1, 2012, eff. Jan. 1, 2013.