The EPA still allows cca to be used to treat lumber, just not in sizes normally used for decking or playscapes. 2x6's & smaller can not be treated with cca, but 2x8's & up can be. Most 6x6's & large timbers are still treated with cca. Although you can get it for 2x8's it is not usually stocked by lumber yards & must be special ordered.
On a side not I used to buy my treated lumber directly from a treatment plant, the old boy that ran the place died of cancer some years ago.