Clayton Cramer has the story here
A lot of people (including Dan Beiser, the bill's sponsor) were surprised that necrophilia isn't already illegal. I'm not. It's Illinois. The state whose largest city is Chicago, where half the skeletons are in politicians' closets and the other half vote. If the voting dead objected to getting it on with the living every once in a while, they'd have lobbied for an anti-necrophilia law ages ago.
I say the Illinois legislature should vote against the bill and put it up for referendum, so the voting dead will have a voice in the matter. Unfortunately, there's always the risk that the voters woudl be overturned by the Ninth Circuit. Not that state legislatures are immune to that sort of thing...