Legal Question in Family Law in Maryland

Unless the issue has been addressed in a settlement agreement or court order, no. What each parent does with the child during their respective times with the child is their business. The standard, as always, is the best interests of the child. If one parent associates with people who would put the child in some kind of danger or otherwise wouldn't be in the child's best interests to be around, that's something a court could address. But unless and until that is done or the parties settle the matter themselves, one parent cannot control the other.