This is what my supervisor told me. We were at the reference desk together. I noticed out of the corner of my eye, a man at one of the teen computers, zip lock bag in hand. He had rolling papers in the other hand that he had just lined. As I observed him rolling the joi.nt, I mentioned it to my boss, and he said, "Since there isn't a policy against a patron rolling a joint, it is allowed!"
So I now know that it is okay for folks to sit in the open and roll joints inside the library.