Just reading what's been quoted in the blog post, this makes it so that an upsell purchase is a distinctly different transaction from a previously completed purchase.
What was possible before:
1. Visitor enters billing information and makes a purchase
2. Visitor is shown an upsell page
3. Visitor clicks a link on the upsell page
4. The item that was clicked is automatically added to the previously completed purchase
Now, step 4 isn't possible. A retailer must make it clear (by virtue of asking for billing info again) that there is a new purchase that's about to happen.
Except that this isn't in the law at all. That scenario is still completely legal. There is no distinctly different transaction unless the upsell was to a different company, and involved that other company separately charging the customer.
What was possible before: 1. Visitor enters billing information and makes a purchase 2. Visitor is shown an upsell page 3. Visitor clicks a link on the upsell page 4. The item that was clicked is automatically added to the previously completed purchase
Now, step 4 isn't possible. A retailer must make it clear (by virtue of asking for billing info again) that there is a new purchase that's about to happen.