It looks like there is official permission in London to exhume some graves for re-use after 75 years, and it's generally accepted that a grave is only owned for a 100 years (that seems to come from the Burial Act of 1857 in the UK).
In general it seems that yes, given sufficient time, the tricky legal problems of exhuming become quite a bit more simple.
It doesn't make sense to say "in Europe" when talking about laws. Eventually "European Union", but the fact that the parent used "Europe" is a signal that it could be simply fake information or a misinformed claims.
Saying "in Europe" is the result of lazyness OR misinformation. In both cases it results on an over-generalization, which can be dangerous. The "snarky reply" is being down voted while it is ACTUALLY TRUE and adds something to the conversation.
For people without downvote right, the only way to disagree is to post a comment, which is then downvoted... See the problem there?
It really makes you wonder how many facts, stories or anecdotes are voluntary or involuntary made up on HN.