There are no legal issues with removing them. The manufacturer is required to put them there, but you have no such liabilities when selling your car used.
Removing them may be a little bit of a tedious or messy process, but it's entirely possible. Just go to the store and buy something called "sticker shock" or you can use "Goo Gone". WD40 works pretty good too. Saturate the sticker completely and let it soak in for a few minutes (needs to get down to the bottom. Then use your fingernails or a straight blade to remove the sticker. Once the sticker itself is off, any residual glue can be remove by soaking it a little more and using fast orange or simple green and a scrub brush.
Just be careful with any of those cleaning chemicals accidently dripping onto your leather, cloth, or carpet. It won't hurt anything if it does, but you'll want to get it off with a towel and some water pretty quickly, or the spot may discolor. Plastics will be unaffected, however.