Md. Code, Family Law § 9–202

(a) The court may modify, in accordance with the provisions of this subtitle, a child custody or visitation order if the court determines that there has been a material change in circumstances since the issuance of the order that relates to the needs of the child or the ability of the parents to meet those needs and that modifying the order is in the best interest of the child.

(b) A parent’s proposal to relocate the residence of the parent or the child in a way that would cause physical custody to be impracticable constitutes a material change in circumstances.