Things like this used to be what the officer's discretion was for. It used to be that "inhumane treatment" was used on a case by case for prisoners who would take advantage if treated normally (shackles for the prisoner who will run if not shackled, toilet paper instead of tampons for the prisoner that will do I don't know what if given tampons, etc.). Over time these things became the default and decent treatment became the exception rather than the norm. Therefore we didn't used to need a law but we do now.