[dmbass]

in a drug bust, it's pretty cut and dry as to whether the targets are doing something illegal

That's way too subjective for law. The prosecution has to prove to the jury (NOT the judge) that what they found is, in a criminal case, beyond a reasonable doubt, an illegal substance.

[comicjk]

Not exactly difficult. A chemist with a mass spec could prove it in 5 minutes. Proving willful noncompliance with the dmca is a whole different league of problem.