EWTN Catholic Q&A
Can the Pope be taken out of grave?
Question from Marie on 04-19-2005:

I heard from my brother that the popes were untouchable after they were buried, meaning they couldn't be taken out to see if they are incorruptible etc. Is this true? Marie

Answer by Colin B. Donovan, STL on 05-04-2005:

No, that is not true. John XXIII's tomb was opened, and his body moved, into the Basilica itself after his beatification. The living pope has supreme authority, so whoever is pope at a particular time is always free to decide what to do with the remains of his predecessors. Obviously, they would take into account the wishes of the former pope, but they would also have to consider the common good of the Church - such as to allow liturgical veneration of the remains as was done in John XXIII's case.