I know youre sick of talking about diabolists but.....

[Cranus]

If the permanent ward is active, it can't be removed...

Well, there is an extrapolated way, but it involves lots of damage all around...

Otherwise, it depends on whether or not the bone is still intact from the removal process.

[Veknironth]

Well, I agree with Cranus. The whole point of having a permanent ward is for it to never be unactive.

-Vek
"Only permament some of the time."

[Borast]

However, with access to a certain Spell of Legend, you could temporarily neutralise the ward and disassemble it to obtain the dragon bone.

BUT, if you're high enough of a level to cast that sort of spell, you can just go out and kill a dragon (or demon, since they tend to be easier to kill) each time. But you wouldn't need to worry about it much!