Why is it against federal (?) law to remove a matress tag?

Question

thanks for the answers

Answer 1

as the consumer, you can remove it.  

it is illegal for dealers to remove because the tag has info that you, the consumer, have a right to no (manufacturing location and materials, fire rating, etc.)  It used to be the case that noone could remove a tag but it has changed, at least here.

Answer 2

A law label is a legally required tag or label on new items describing the fabric and filling regulating the United States mattress, upholstery and stuffed article (eg: pillows, plush toys, comforters, etc) industry. Typically these tags begin with a phrase such as This tag may not be removed under penalty of law except by the consumer. Some states require tags on used bedding as well.

Laws requiring these tags were passed in the United States to inform consumers as to whether the stuffed article they were buying contained new or recycled materials. This was and still is considered important as contaminated, recycled stuffing material could contain lice, bedbugs, or human excretions.[citation needed]

Such stuffed article labelling laws exist in other jurisdictions, for example, the tag required on duvets sold in the United Kingdom, that describe the materials used and the tog insulation rating.