phat im confused. would you say its biblical to pray to my dead grandmother? or to ask for her to pray for me? i havent been in this thread for a minute. lol.As a personal devotion, that would be ok. In other words, you can pray to her yourself, but you can't encourage or advertise prayers to her as a devotion for the whole Church. Then it becomes public devotion, or "popular piety", and that is regulated by the Magisterium.
Once the Church beatifies a person, the group of Catholics that propagated that person's cause for sainthood, or who have a particularly strong connection to him (usually b/c they are from the same country/region/religous order as he is) are allowed to pray to him. Once that person is canonized, the universal Church is permitted to do the same.
This regulation is meant to safeguard the piety of the Church's members and to ensure that this piety is always properly ordered (which is a very good and pastoral thing to do). You don't want Catholics praying to someone who did not exhibit true, heroic virtue, or, even worse, who lived a life of faithlessness.
I hope that answers your question.
ps: To anticipate a possible misunderstanding, the Catholic Church does not "make" people saints, as if they weren't in heaven w/ God until the Church said so. Instead, She simply confirms what was already made so by God, as soon as He judged that person fit for heaven.