This is absolutely why many copyright stumpers try to frame fair use as an affirmative defence. It complicates schemes like this, where automated tools/manual takedown companies (aka tools) are very very bad at discerning fair use, hence they (severe copyright enforcement types) want to make it not their problem.
The problem with it as an affirmative defence is that engage to protect this involves lawyers and lawsuits to get content unblocked and that, to date, this has not resulted in fees.
Isn't the police dept as a whole responsible for ensuring their field tests are reliable? I get maybe not holding individual cops responsible in this instance (the switch from looking for a grow op to looking for personal use notwithstanding), but the dept should have a responsibility to ensure their forensic tests are accurate. Otherwise, tests which are notorious for false positives become probable cause factories.
Strong encryption is out of the bag, and short of major evolutions in quantum computing or solving the whole P vs NP thing, there's no getting around it.
The oldies have (re)fallen into the trap of thinking technology comes from a place invented by a guy named "Head of Technology". Technology is sometimes messy and organic in its evolution, it defies control.
Even if they get Apple and Google and Microsoft and, and, and to backdoor encryption, the motivated will use (and evolve) OSS crypto tools, and the motivated include the bad guys. Those "common folk" not skilled enough to leverage this will be left with their asses in the wind.