There's probably scores of places, that if you asked enough questions, of enough bored pencil pusher archies, using key words like "artifact", 'take" and "indian bone", that ..... yes: You'd be told "no". Then we md'rs spread the word around through our writings, posts, etc... that "such & such place is off-limits". Perhaps by specifics. Or perhaps only by ancillary wording regarding "cultural heritage" or "take & remove", etc.....
But sometimes I hear of someone who's gone to such places who simply didn't know any better. NOT TALKING ABOUT HISTORIC SENSITIVE MONUMENTS, but just regular routine beaches (that .... gasp .... are federal?). And lo & behold, they hunted for months or years, and no one ever said so much as "boo" to them. Yup, right in front of rangers, etc..... who never gave them anything but a friendly wave. Imagine their surprise when someone in the md'ing community said "I thought that was off-limits" ? At first they assume the person telling that must be mistaken. Because *certainly* if that were true, then someone would have said something by now, eh ?