Legal Question in Family Law in Maryland

It is not possible to answer your question without more information. What is the basis for his request to modify legal custody? Assuming there is a court order in effect regarding custody, he can ony obtain a change in custody by proving that there has been a material change in circumstances and then, after meeting that burden, by establishing that a change in custody is in the child's best interest. Since joint legal custody requires that you and he make material decisions for your child together, has there been a history of an inability to do so?