Maryland Family Law Section 10-307

      (a)      A tribunal of this State may exercise jurisdiction to establish a support order if the complaint or comparable pleading is filed after a complaint or comparable pleading is filed in another state only if:

            (1)      the complaint or comparable pleading in this State is filed before the expiration of the time allowed in the other state for filing a responsive pleading challenging the exercise of jurisdiction by the other state;

            (2)      the contesting party timely challenges the exercise of jurisdiction in the other state; and

            (3)      if relevant, this State is the home state of the child.

      (b)      A tribunal of this State may not exercise jurisdiction to establish a support order if the complaint or comparable pleading is filed before a complaint or comparable pleading is filed in another state if:

            (1)      the complaint or comparable pleading in the other state is filed before the expiration of the time allowed in this State for filing a responsive pleading challenging the exercise of jurisdiction by this State;

            (2)      the contesting party timely challenges the exercise of jurisdiction in this State; and

            (3)      if relevant, the other state is the home state of the child.