In the new Rolling Stone Keith Richard is quoted as saying he ground up some of his deceased father's ashes and snorted them with some cocaine.
He said it "went down really easy". Is this like a weird form of cannibalism?

Would it be really sh*t for me to give a scientific answer and show me up as a pedant? I hope not because here comes the science bit

I say no, it's not cannibalism as that which was once his father has been tranformed, via the energetic medium of fire into a different form, mainly Carbon. It's similar to why eating plants that have gained nutrients from the soil that came from decomposed human bodies isn't cannibalism, via a chemical means the body matter has been transformed and is no longer human flesh.

Besides, isn't cannibalism just eating people, not snorting them? That legal loophole may well succeed where my previous defense fails

Not sure about that - but it's the best headline since "Freddie Starr ate my hamster" !

I know someone who did this as well. I found it very disturbing, it would appear to not be that uncommon.