Which jurisdictions are these? Googling "used mattress illegal" returns this post as the seventh result, and most of the other results (such as https://www.consumer.ftc.gov/articles/0099-shopping-used-mat...) seem to indicate there are only restrictions on labelling or processing.
“For example, in many places, old mattresses that have been recovered with new ticking (strong, tightly woven cotton or linen fabric) can be sold as long as they are sanitized or disinfected in some way before sale. In other states, only certain parts of mattresses, such as the springs, can be reused.“
