There have been several diaries and a lot of discussion recently on the ballot initiative that is going to be voted on in California in June. The actual ballot initiative can be found here.
The key text in this initiative comes in the proposed Section 6902(b):
An elector shall be elected in each congressional district if the candidate to whom that elector has pledged to vote received a plurality of the popular vote cast in that congressional district. The two at-large electors shall be elected if the candidates to whom those electors have pledged to vote received a plurality of the popular vote cast in the state.
If you'll follow me over the fold, we'll see just why this is illegal.