Grandparents' rights are not what many people seem think they are. It's not a court ordering a couple to let estranged/toxic grandparents have access to their grandkids above the objections of the parents.
Rather, it is adjusting custody arrangements during separation/divorce so that grandparents can maintain an existing relationship wth their grandkids. For example, if a couple is separating and the mother gains primary custody, the father's parents can apply to get visitation rights with the kids. It's not automatic, as they would have to meet the burden of, "in the best interest of the children," to the satisfaction of the judge.
Disclaimer: I am not a lawyer, but this is my understanding of the issue from reading discussions and papers (including the one linked in another post in this thread).