Drug paraphernalia is specifically defined under federal law, in Title 21 of the US Code, the same title that list and defines what are controlled substances:
TITLE 21 >
CHAPTER 13 >
SUBCHAPTER I >
Part D > § 863
(d)
“Drug paraphernalia” defined
The term “drug paraphernalia” means any equipment, product, or material of any kind which is primarily intended or designed for use in manufacturing, compounding, converting, concealing, producing, processing, preparing, injecting, ingesting, inhaling, or otherwise introducing into the human body a controlled substance, possession of which is unlawful under this subchapter. It includes items primarily intended or designed for use in ingesting, inhaling, or otherwise introducing marijuana,
[1] ......., hashish, hashish oil, PCP, methamphetamine, or amphetamines into the human body, such as—
(1) metal, wooden, acrylic, glass, stone, plastic, or ceramic pipes with or without screens, permanent screens, hashish heads, or punctured metal bowls;
(2) water pipes;
(3) carburetion tubes and devices;
(4) smoking and carburetion masks;
(5) roach clips: meaning objects used to hold burning material, such as a marihuana cigarette, that has become too small or too short to be held in the hand;
(6) miniature spoons with level capacities of one-tenth cubic centimeter or less;
(7) chamber pipes;
(8) carburetor pipes;
(9) electric pipes;
(10) air-driven pipes;
(11) chillums;
(12) bongs;
(13) ice pipes or chillers;
(14) wired cigarette papers; or
(15) ....... freebase kits.
(e) Matters considered in determination of what constitutes drug paraphernalia
In determining whether an item constitutes drug paraphernalia, in addition to all other logically relevant factors, the following may be considered:
(1) instructions, oral or written, provided with the item concerning its use;
(2) descriptive materials accompanying the item which explain or depict its use;
(3) national and local advertising concerning its use;
(4) the manner in which the item is displayed for sale;
(5) whether the owner, or anyone in control of the item, is a legitimate supplier of like or related items to the community, such as a licensed distributor or dealer of tobacco products;
(6) direct or circumstantial evidence of the ratio of sales of the item(s) to the total sales of the business enterprise;
(7) the existence and scope of legitimate uses of the item in the community; and
(8) expert testimony concerning its use.
US CODE: Title 21,863. Drug paraphernalia
Each state has its own definition of "drug paraphernalia" for purposes of state penal codes, but I guarantee you they will all similarly hinge on the "primarily designed for" and "primarily intended for" use of any controlled substance, the possession of which is unlawful.
But as you can see, the most relevant part of the above to this discussion is the section e, listing the factors that help to determine whether an item is parahernalia, or not.
For those same sorts of factors are the ones that can be applied, for example, to a determination whether an ecig should be considered a "drug device" or not, but in the very different context of a non-controlled substance like nicotine, or even no nic liquid.
