So Merchant X - a perfect fit for one of my sites, solicited me to join their program.

I joined but did not put up any links right away. I received another solicitation, and responded by saying that I had joined, and would soon start promoting their products.

A few days later, I began adding links to one section of the relevant site. I then received this email, on July 12:
Dear Affiliate,

Due to recent changes in the affiliate nexus regulations and your state local laws we will be unable to maintain our affiliate/merchant relationship. As of July 12, 2012 your account with Merchant X via ShareASale, will be removed from our affiliate program. We sincerely apologize for the inconvenience and in the future if local regulations for your state change please do not hesitate to re-apply. Thanks.

Merchant X Affiliate Manager
I responded the same day, as follows:
Dear Merchant X Affiliate Manager,

There has been no change to "affiliate nexus regulations" in California since last September, and it is purely speculation as to whether or not the affiliate nexus law enacted last July will ever go into effect.

I must also add that after receiving invitations to join the Merchant X program and then doing so, and then just now beginning to add product links, Zero days notice of this termination, for a reason that makes no sense, is unreasonable.

I have received no reply (12 days have passed).

So did he suddenly figure out that CA passed an affiliate nexus law A YEAR AGO? Guess I'll never know.