Last night California governor Jerry Brown signed a new law that will enforce sales tax for online retailers, prompting Amazon to end its affiliate program in the state.

The Los Angeles Times has more about the law: “The online sales tax law, AB 28 1x, would seek to force online retailers who have no physical presence in California, such as Amazon.com, to collect the same levies as bricks-and-mortar stores. Lawmakers calculated it would net the state $200 million. Retailers from Wal-Mart to mom-and-pop bookstores had pressed for the tax law rewrite.”

Amazon has already modified its operating agreement for affiliates linking to Amazon products on their sites: “if at any time following your enrollment in the Program you become a resident of California, Colorado, Illinois, North Carolina, Rhode Island, or Connecticut, you will become ineligible to participate in the Program.” Over at BoingBoing, you can read a complete copy of Amazon’s letter to affiliates that called the new tax bill “unconstitutional and counterproductive.”