SF STORY PREMISE:

SETI program decodes an alien signal clearly targeting us.

Hi! We see you're still facing the Great Filter! We want to help! Based on your anatomy per broadcasts we decoded, here is a blueprint for a device that will solve your problem!

Humans: decode blueprint.

It's for an improved guillotine.

@cstross Fantasy story premise. A wizard casts a spell such that each week (day?) the richest person in the world dies. (It's magic, it can work out what that means and who that is.) And then ... ?
@dearlove @cstross this this the single-law world fix.
Yearly we take the Forbes list, ans whoever is number one gets taken out. All of their wealth is forfeit and used to fund the UN and redistributed to the world's poorest. After a few years of this, nobody wants to be obscenely rich and the worlds poor are no more. Probably this fixes climate change as well.