I think this is the law. They might not have to tell, but they have to mark the equipment as such
I think it is only the law if you buy something. Directv tries to let people know they are not buying receivers when they pay for them
When you receive a replacement wireless router, cell phone or whatever under the warranty, they don't mark them reconditioned even when they clearly are. I had a wireless router replaced last year and it was packaged as if it was new but there were some marks where someone had obviously wall mounted it.
A friend just recently had his GS4 replaced and was unhappy that there was a small scratch on the back, called to complain, and was told that they will ship either new or reconditioned phones at their option, and don't consider minor cosmetic defects to be a valid reason to exchange. He remembered me mentioning I'd my iPhone 5 replaced last year (sleep/wake button was not working reliably) and asked if I'd been shipped a reconditioned phone and I told him I had no idea. It was packaged like new, and looked/worked like new, but for all I know it might have been reconditioned. I've heard when Apple reconditions phones they replace the entire case (front and back) and the battery, so I can't think of a way you could possibly tell unless they marked them.
Some people will make the argument that it is better to get a reconditioned product than a new one, since they usually go through a lot more testing. Most companies assume something that's new works properly and don't give it much testing!
SL5, PI-6S, SA-6AL 3xSWM16, 21 H20-100, 1 H20-600, 7 H24-700/AM21