In the early 20th century, organic material such as straw, leaves, pine
needles and reeds were used to stuff mattresses. Over time, these materials
would rot and mold, and become a haven for vermin (hence the origin of
the saying "don't let the bed bugs bite").
So that consumers could make informed decisions about which mattress to
buy, the U.S. Government passed a law that required mattress manufacturers
to disclose the contents of the mattress on a tag. A companion law forbid
manufacturers and sellers from removing these tags. The consumer, however,
is free to do so. So while the tag's warning is quite stern it does
not apply to consumers and you may go ahead and ignore it without fear
of criminal prosecution (but do still watch out for bed bugs!).