One of the questions communitarians raise about Rawlsian liberalism has to do with the state’s assumed position of neutrality toward questions of the good or the good life. This “neutrality of aim,” as Rawls will call it, is what he refers to when he explains that political liberalism prioritizes the right over the good. This doesn’t mean that rights are not related to the good. It means that the individual’s right to choose for herself a particular conception of the good life (within limits, such as short of infringing upon another’s rights) has structural priority over any particular conception of the good life.
On one hand such neutrality is obvious. For political liberalism, diversity of thought concerning what constitutes the good life is part of the aim. Such diversity will be encouraged and permitted insofar as it doesn’t violate a structural standard/norm, such as an individual right. Yet I think the communitarians point out a legitimate weakness in such neutrality.
To clarify what I mean by neutrality here we should look at what Rawls says on the topic. Rawls deals with this most directly (that I’ve found) in a 1988 article entitled “The Priority of the Right and Ideas of the Good.”  Here he discusses the issue of neutrality (apologies for the rather long quote):
Thus, neutrality might mean, for example, (1) that the state is to ensure for all citizens equal opportunity to advance any conception of the good they freely affirm; (2) that the state is not to do anything intended to favor or promote any particular comprehensive doctrine rather than another, or to give greater assistance to those who pursue it; (3) that the state is not to do anything that makes it more likely that individuals will accept any particular conception rather than another unless steps are taken to cancel, or to compensate, for the effects of policies that do this.
The priority of right excludes the first meaning of neutrality of aim, for it allows only permissible conceptions (those that respect the principles of justice) to be pursued. But that meaning can be amended to allow for this; as thus amended, the state is to secure equal opportunity to advance any permissible conception. In this case, depending on the meaning of equal opportunity, justice as fairness may be neutral in aim. As for the second meaning, it is satisfied in virtue of the features of a political conception: so long as the basic structure is regulated by such a view, its institutions are not intended to favor any comprehensive doctrine. But in regard to the third meaning (considered further in Section VI below), it is surely impossible for the basic structure of a just constitutional regime not to have important effects and influences on which comprehensive doctrines endure and gain adherents over time, and it is futile to try to counteract these effects and influences, or even to ascertain for political purposes how deep and pervasive they are. We must accept the facts of common-sense political sociology.
To summarize: we may distinguish procedural neutrality from neutrality of aim, but the latter is not to be confused with neutrality of effect or influence. As a political conception for the basic structure justice as fairness as a while can be seen as exemplifying a kind of procedural neutrality, and it also hopes to satisfy neutrality of aim in the sense that the basic institutions and public policy are not to be designed to favor any comprehensive doctrine. Neutrality of effect or influence political liberalism abandons as impracticable, and since this idea is strongly suggested by the term itself, this is a reason for avoiding it.
But even if political liberalism can be seen as neutral in procedure and in aim, it is important to emphasize that it may still affirm the superiority of certain forms of moral character and encourage certain moral virtues. Thus, justice as fairness includes an account of certain political virtues – the virtues of fair social cooperation such as civility and tolerance, reasonableness and the sense of fairness. The crucial point here is that admitting these virtues into a political conception does not lead to the perfectionist state of a comprehensive doctrine. 
Rawls asserts that his form of liberalism assumes neutrality in procedure and aim.
The point of this post comes down to Rawls’ statement that political liberalism, “hopes to satisfy neutrality of aim in the sense that the basic institutions and public policy are not to be designed to favor any comprehensive doctrine.” What exactly he means by “comprehensive doctrine” is not clear to me, but it seems he is saying that political liberalism resists the promotion or enforcement of any particular notion of the good life by the state or its laws.
Instead by virtue of its parameters a limited diversity of definitions of the good life are allowed, certain sorts are encouraged, but no one view is promoted. This seems perfectly rational and internally consistent, valuing diversity and allowing for a number of different conceptions of how to live.
Yet I think I align with some critics of liberalism who might assert that sometimes the state ought to promote and perhaps even enforce (laws because of) a particular conception of the good or the good life, be it individual/personal or social/common. That is, such a view contends that sometimes a particular conception of the good ought to supersede or have “priority” over the right (namely the right to choose a definition of the good, within certain perimeters, for one’s self).
Functionally it seems liberal democracies do in fact muddy these waters anyway, transgressing their ideological purity (but who is pure, after all?). For example, on what grounds can a liberal state prohibit the use of the hardest and most dangerous drugs?  I would agree that such substances should be prohibited – although I would opt for their use being decriminalized, treated as a public health issue instead of a criminal one – but I see no liberal grounds upon which to do so.
A consequentialist case could be made that the widespread use of drugs would completely undermine the necessary social institutions of a society and disrupt law and order, resulting in an ungovernable state. While this pragmatic argument has a certain force, is the only reason for their prohibition simply that their use will make people unruly? Is the purpose of laws/legislation only to hold off chaos?
Interestingly such consequentialist calculation is precisely one of the things the tradition of liberal rights is supposed to prevent. That is, one of the real strengths and promises of such a tradition is the establishement of inviolable individual rights which protect from overreaching state or majority power (esp. in the form of laws). So long as a fair and mutually agreed upon transaction has been made between two reasonable adults, on what grounds can a liberal state prohibit certain sorts that don’t violate an individual’s right to free and fair economic exchange? It seems one would have to say that free and unfettered access to and participation in an economic exchange of one’s choosing isn’t itself actually a right, which it doesn’t seem many liberals would want to admit.
A different case could be made that drugs should be dealt with in a particular way because that way is the best way to get rid of them or lessen their impact. Such an argument, it should be noted, is not a consequentialist one. Instead it is the utilization of pragmatic means to achieve a particular end, an end which almost inevitably has in mind a particular conception of the good (that is, a conception which is incompatible with drug use). So while I may have issue with the pragmatists line of thinking in parts, it is equally at odds with Rawlsian neutrality of aim.
However I would argue that the hardest drugs are problematic for a society because such substances (outside of a medically controlled environment) are perhaps uniquely powerful in their corrosiveness on the dignity of an individual because of the combination of their severe effects on physical and mental health and the enormity of their destructive force upon social and relational commitments. That is, they should be prohibited because their use so severely inhibits one’s ability to be most human, to live a full life – to live up to one’s civic duty, social obligations, and relationships. It is therefore because of this reason that such drugs are so insidious, and because of this that they degrade the common good, not merely the common’s governability.
It seems that this reason would be a violation of Rawls’ neutrality of aim, for to utilize it the state would need to support, at least partially, some specific understanding of the good or the good life, giving it priority over an individual’s right.
Does such reasoning lead to a slippery slope? What about all the other activities that are corrosive of the good life, why not prohibit those? Practically it would be impossible to prohibit all of them, and simply because some sense of the good life is promoted doesn’t mean no room for diversity of views can be made. But perhaps some activities are simply too corrosive of the good life and the common good, meaning they deserve the special attention of prohibition. This is of course somewhat arbitrary, but not entirely so. And yet I would suppose that if there were indeed many other activities that are as corrosive as, say, heroin use, that we should at least engage in public disputes about their acceptance in society.
I suppose it comes down to this, for me: if Rawls is saying that a politically liberal state must allow for all individual decisions of the good life insofar as they don’t violate another’s right to do so, then I think his idea needs addressing. If Rawls is willing to allow for legislation on the grounds listed three paragraphs above, then my critique is off base. While I’m not trying to dismiss liberalism out right, it seems upon my initial readings of Rawls that he wouldn’t allow for it.
 This article was originally published in the journal Philosophy and Public Affairs, reprinted in his Collected Papers.
 John Rawls, “The Priority of the Right and Ideas of the Good,” Collected Papers, 459-460.
 The line must be drawn somewhere, between the sort of substances that are so dangerous and destructive, and those that are largely harmless and recreational. I suppose part of that distinction is always arbitrary, but it should be rooted in science, etc.