Composition laws via stacks

Composition law paper todo:

a) Go over composition law proofs

b) Think about applications to composition laws

 - do comp laws hold over arbitrary rings?

 - try to use the "kernel thing" to generate new composition laws. (Need non-special groups. The usual setup uses pre-homogenous spaces. Maybe find some 'near misses' -- i.e., setups that people don't study because they don't give PHV's

 - I don't really understand yet how people use composition laws to prove other cool theorems.

 - Melanie and Dan's paper, references to Melanie's thesis, etc