To sum up from the article: If you want to grow opium poppies (for flowers or seeds for baking), that's just fine as long as you don't know that's what you're doing. So, as Pollan advises, simply stop reading about poppies. If, however, you do know that your poppies could be used to make opium, you are probably guilty of breaking the law.
The article, published in 1997, describes federal agents leaning heavily on seed companies to stop carrying Papaver somniferum, the opium poppy. Over ten years later, Cook's Garden and Thompson & Morgan are still carrying the seeds, so perhaps clear heads have prevailed.
Now I will say that baking seed poppies are not the same as opium poppies (although they are botanically identical). That information (misinformation?) now frees you to grow them completely legally!