There is a difference between synthesized and naturally occurring substances. For example, vitamin c and thc are far superior if sourced directly from fruit or plants as opposed to being made in a lab, like ascorbic acid and marinol.
From what I remember, natural vitamin c, for example, also contains many other compounds that are not present when synthesized. I don't know about adrenalchrome specifically; just assuming that if made in a lab, it is likely not exactly the same as when extracted from a terrorized person, possibly lacking certain elements.
Since they have broken every law known to man while on U.S. soil, one must wonder what the hell else could they be doing to require such a legal buffer.