I wouldn’t say it’s bad law, but it certainly is an area that the courts have struggled with. The dissents in the obscenity cases that came after Millerdemonstrate that some Justices had real misgivings about not just the feasibility of applying the three prong test, but even about the constitutionality of banning obscene materials! For example, in Pope v. Illinois, the dissenting Justices (and even Scalia in his concurrence) had some fairly scathing things to say about the Miller test and even the idea that obscene materials were outside First Amendment protections:
[QUOTE=Justice Scalia]
I join the Court’s opinion with regard to an “objective” or “reasonable person” test of “serious literary, artistic, political, or scientific value,” Miller v. California, 413 U. S. 15, 24 (1973), because I think that the most faithful assessment of what Miller intended, and because we have not been asked to reconsider Miller in the present case. I must note, however, that in my view it is quite impossible to come to an objective assessment of (at least) literary or artistic value, there being many accomplished people who have found literature in Dada, and art in the replication of a soup can.
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[QUOTE=Justice Brennan]
I write separately only to reiterate my view that any regulation of such material with respect to consenting adults suffers from the defect that “the concept of `obscenity’ cannot be defined with sufficient specificity and clarity to provide fair notice to persons who create and distribute sexually oriented materials, to prevent substantial erosion of protected speech as a byproduct of the attempt to suppress unprotected speech, and to avoid very costly institutional harms.” Paris Adult Theatre I v. Slaton, 413 U. S. 49, 103 (1973) (BRENNAN, J., dissenting).
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[QUOTE=Justice Stevens]
The Court correctly holds that the juries that convicted petitioners were given erroneous instructions on one of the three essential elements of an obscenity conviction. Nevertheless, I disagree with its disposition of the case for three separate reasons: (1) the error in the instructions was not harmless; (2) the Court’s attempt to clarify the constitutional definition of obscenity is not faithful to the First Amendment; and (3) I do not believe Illinois may criminalize the sale of magazines to consenting adults who enjoy the constitutional right to read and possess them.
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In fact, Justice Stevens brings up the exact concern that the OP raises: how can an individual know he is breaking the law when the law is so vague?
[QUOTE=Justice Stevens]
The Court has repeatedly recognized that the Constitution “requires that a penal statute define the criminal offense with sufficient definiteness that ordinary people can understand what conduct is prohibited and in a manner that does not encourage arbitrary and discriminatory enforcement.” Kolender v. Lawson, 461 U. S. 352, 357 (1983). These two requirements serve overlapping functions. Not only do vague statutes tend to give rise to selective and arbitrary prosecution, but selective and arbitrary prosecution often lessens the degree to which an actor is on notice that his or her conduct is illegal.
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So clearly the judicial reasoning in this area of law is fragmented, even if Miller remains good law in the sense it is still valid law. But now that the internet has changed how people access materials, the Miller Test is due for some clarification (as the Ninth Circuit has already done in US v. Kilbride, mentioned by another poster in the other thread).