I’m all in favor of the decriminalization of marijuana, indeed for the eventual legalization of recreational pot use, but the closer we come to achieving that goal, the greater the number of practical quasi-dilemmas we’ll have to face that we’d never had to consider before. These quasi-dilemmas may not be conclusive considerations against full legalization, but they can’t be minimized, either.

It’s common for advocates of legalization to compare pot with alcohol: if we accept recreational alcohol consumption, why not accept recreational consumption of pot? In many ways (it’s plausibly argued), alcohol is worse than pot. If we overlook the problems with alcohol and allow recreational alcohol consumption anyway, it seems inconsistent to fixate on the similar problems with pot in order to ban the recreational use of pot.

Any reasonable person would grant that alcohol sometimes has problematic, indeed lethal effects in certain contexts–DUI/DWI, for instance. But the right way of dealing with those consequences (it’s argued) is to regulate alcohol consumption, not to prohibit it altogether. So when it comes to DUI/DWI, in the U.S. at least, we stipulate that a blood alcohol content (BAC) of 0.08% (or 0.04% for commercial drivers) is the relevant threshold: a BAC of 0.08%/0.04% is legally incompatible with driving, while a BAC lower than that is, though inadvisable, not legally actionable.

Reliance on a specific BAC is essential to the way the law is currently written. We don’t criminalize the sheer consumption of alcohol; we criminalize impaired driving by way of BAC levels. And in doing so, we insist on a precise, measurable, and quantifiable standard rather than on impressionistic behavioral judgments about who is “drunk” and who isn’t. Surely, the argument continues, we can do the same with the consumption of pot?

The argument is less straightforward than you might think even when it comes to alcohol (think Indian reservations, public intoxication), but accept it for the sake of argument. The problem is that as things stand, we can’t “do the same with the consumption of pot”: there is no precise, measurable, quantifiable way of determining when a pot smoker is the functional equivalent of a drunk driver. From the Wikipedia entry on “cannabis testing”:.

Unlike alcohol, for which impairment can be reasonably measured using a breathalyser (and confirmed with a blood alcohol content measurement), valid detection for cannabis is time-consuming, and tests cannot determine an approximate degree of impairment. The lack of suitable tests and agreed-upon intoxication levels is an issue in the legality of cannabis debate, especially regarding intoxicated driving.

The concentrations obtained from such analyses can often be helpful in distinguishing active use from passive exposure, elapsed time since use, and extent or duration of use.

The Duquenois-Levine test is commonly used as a screening test in the field, but it cannot definitively confirm the presence of cannabis, as a large range of substances have been shown to give false positives.

So while you can test for the sheer presence of cannabis in someone’s bloodstream, there is no existing field-deployable test that tests for the precise level of cannabis that demonstrates the sort of impairment that would (or ought to) be legally actionable. Someone might, of course, devise one at some point. And I hope they do, soon. But it’s an interesting and worthwhile question whether efforts at legalization ought to be paused or slowed down until they do.

Put it this way: would we so easily accept the permissibility of recreational alcohol consumption if we had no feasible way of enforcing laws against DUI or DWI? Deprived of blood alcohol tests of the modern variety, what feasible method of enforcing those laws would we have?

Like all dilemmas, this one points in at least two directions. Suppose that we allowed recreational alcohol use while lacking precise tests for blood alcohol level. In that case, we might

(1) …still have laws against DUI/DWI, but only have rough, qualitative ways of establishing a causal relationship between a given suspect’s degree of inebriation and her degree of impairment. Such coarse grained procedures would be problematically conviction-prone: they would, in an uncomfortably large number of cases, result in the convictions of people who might otherwise have gone free (i.e., suspects whose BAC was <0.08% in the ordinary-driver case, or <0.04% in the case of holders of commercial driver’s licenses).

If you find it intolerable that innocent people should be punished on essentially consequentialist grounds for crimes they haven’t quite committed, this horn of the dilemma is going to be problematic.

(2) On the other hand, we might find such a conviction-prone system intolerable, and do away with laws against DUI/DWI until such a time as we’d devised the sort of test that could demonstrate guilt beyond a reasonable doubt.

That, of course, would undoubtedly incentivize drunk driving, and lead to an increased incidence of alcohol-fueled accidents, injuries, and deaths. But if you’re the kind of person offended by pie-in-the-sky deontologists who are willing to let innocent people die in order to uphold the procedural rights of technically innocent people who are still doing untoward things, this horn of the dilemma is going to bother you.

A reasonable intermediate option, I suppose, would be to retain the conviction-prone system (as per point 1 above), resign ourselves to its conviction-prone nature, but downgrade the convictions involved to misdemeanors, or maybe even to mere administrative offenses, rendering wrongful convictions more tolerable while still sending the desired message about the illegality and inadvisability of the target behavior. This is more or less the view already taken in the enforcement of laws against public intoxication. Predictably, such laws are often (justifiably) thought to be enforced in a discriminatory or arbitrary way. Of course, it might also reasonably be argued that this “intermediate” approach just dilutes the preceding problems without resolving any of them.

I think of this reasonable intermediate option as, at some level, foreseeably (though not intentionally) penalizing sheer pot consumption (and in that sense a case of something like decriminalization rather than full legalization). In adopting it, we’d have to acknowledge that some people are going to be penalized for smoking pot and having it in their systems, even if it isn’t certain that their doing so impairs their driving. (Of course, in adopting procedures based on the Fourth, Fifth, and Sixth Amendments, we also foreseeably err in the reverse direction, allowing people guilty of DUI to go free on technical, procedural grounds.) One way to handle this might be to say that in driving on the roads, you implicitly consent to the most reasonable way of handling DUI issues. If the reasonable intermediate option is the most reasonable, you can be thought implicitly to be consenting to it. (And if it isn’t, you aren’t.) But in implicitly consenting to it, you assume the risks inherent in it, including imprecision in its application.

That said, the reasonable intermediate option seems unavoidable, if only because there are so many other substances out there that might impair driving, and there aren’t going to be precise tests for all of them. We can’t prohibit them all, but we can’t allow people to drive on them with impunity, either–whether we have precise tests for them or not.

Notice that the grounds for prohibition in the “reasonable intermediate option” would be rights-based rather than strictly paternalistic. We wouldn’t be making recreational alcohol use illegal because it’s bad or immoral per se, but because it’s risky: it imposes an undue risk on others that we have no better way of preventing, regulating, or policing. And the risks it produces are rights-violative: I would say that a drunk driver who hits you has, through culpable negligence, crossed certain boundaries that violate your rights. If (as I think) we can force people to get immunized, or prevent them from acquiring certain inherently dangerous substances (e.g., explosives, heavy weapons), maybe the dangers of drunk driving suggest a similar rationale for alcohol prohibition, at least in cases where we lack any other adequate means of dealing with it.*

If the reasonable intermediate option wouldn’t be that unreasonable in the case of alcohol in my thought-experiment, maybe it isn’t that unreasonable in the case of pot in the actual world. The alternative is to allow people to smoke pot; foresee the fact that some of them will drive; foresee the fact that some of those driving will cause accidents, some fatal; and then shrug our shoulders at the preventable deaths that arise–on grounds of “civil liberties” (or grounds of the distinction between killing and letting die), saying that we had to let it happen because we couldn’t rightly violate the rights of pot smokers by convicting them of a crime we had no precise way of detecting. I see the rationale, and might even be willing to sign on to it, but I’d do so reluctantly, and with misgivings. And I’d hate to have to be the person to say any of that at the graveside of the first person to die under the relevant policy. Which is why, once we put aside arguments involving bad faith, there’s at least something to police officials’ recent scare-mongering on this topic.

Of course, the criminalization of pot has a long list of risks and harms I haven’t discussed here (and that cops like to evade altogether). Since I’m the last person to deny that there are downsides, let me repeat: I’m all in favor of decriminalization, and eventually, legalization of pot (at least) on par with alcohol. But the absence of an alcohol-like blood test is one reason for hitting or at least tapping the brakes a bit, slowing down a bit, and thinking things through on pot. There are harms and risks no matter what we do. The aim is to minimize as many of them as possible en route to our preferred destination.

I have to end on a weirdly paradoxical note, however. Having gone out of my way to say all this about the lack of a good blood test for pot, the fact remains that my advice for anyone stopped for DUI/DWI (whether for alcohol or pot) is to refuse to take a field sobriety or roadside test at the scene, and…to demand a blood test, even if doing so requires being taken to the police station (as it should, since it’s better to do the test under controlled conditions than otherwise).**

But didn’t I just finish saying that there’s no precise test for pot? Yeah, I did. My point is simply that you should refuse any request that you have the right to refuse, but comply with any order you are categorically ordered to follow (assuming that you know the difference). At a certain point, if you’re stopped, and you refuse the refusable tests, you will be formally detained and ordered to take a blood test. Take it, I guess. Then call a lawyer, assuming you’re sober enough to operate your phone. And I’m going to assume you are. I mean, what kind of idiot would go for a drive after smoking a joint?

*This may not be your idea of a libertarian side-constraint on the use of force, I realize. Deep, dark confession: I’ve always had trouble with libertarian approaches to risk-imposition, dating back to my uneasy and unresolved reading of Robert Nozick’s uneasy and unresolved discussion of the subject in chapter 4 of Anarchy, State, and Utopia. The unease intensified with Eric Mack’s “Prohibition, Compensation, and Risk,” in J. Paul ed., Reading Nozick, and has had an agonizingly slow half-life.

**Melissa explains why: “No, no, no!” I think that her advice about Preliminary Alcohol Screening tests applies to DRE evaluations at the scene, but I’m not 100% sure. Any lawyers in the house? Sober ones, I mean?

Thanks to Melissa Drabik (the Felician University nursing student, not Melissa Lefkowitz, the attorney) for the passing comment that inspired this post.