Question

From a purely halakhic standpoint, after a divorce, is one parent allowed to prevent the other from meeting with the child? In other words, does each parent have a "right" to remain in contact with his or her child? And what about the grandfather—does he also have a basic right to be in contact with his grandson, such that his son or daughter-in-law may not take that away from him "offhandedly" on the basis of what they themselves see as a trivial reason? I am not asking from a moral standpoint or about what is proper, but whether there is an actual right belonging to the grandfather to have some kind of contact with his grandson, unless certain situations arise or there are sufficient reasons that would revoke that right.