Sending biohazard materials across state lines without proper licensing. You can take a stool sample and send it to a lab, for example, but this is done on behalf of a properly licensed testing lab, in containers approved by DOT and some number of other agencies.
It could be interpreted as a terrorist act.
Maybe you get away with it, and maybe you spend $350K defending yourself in Federal court.
I wouldn’t do it.
Bunk.
If that was true you’d have to buy new underwear every time you traveled from one state to another.
Besides it said used underwear not dirty underwear.