From the FDA's website:
Legal Requirements for the Sale and Purchase of Drug Products.
Each state has their own regulations. In Oregon, it's only available by prescription. When I go to Florida, it's behind the counter, handed to me by the pharmacist. They take your I.D. for the electronic log.
When I go to Mexico, I transfer it out of the original packaging to another prescription pill bottle labeled as something else. Sudafed or something containing pseudoephedrine is part of my dive med kit. Sudafed PE contains phenylephrine, which is not the same and is not as effective as psueodoephedrine, as told to me by a pharmacist.