The U.S. Supreme Court granted certiorari to Miller because the California statute at issue was based on two previous obscenity precedents that the Court wanted to revisit. Chief Justice Warren Burger believed that the Court's obscenity jurisprudence was misguided and that governments should be given more leeway to ban obscene materials. Burger pushed for a looser definition of "obscenity" which would allow local prosecutions. Meanwhile, Justice William J. Brennan, Jr., pushed for First Amendment protection for all "obscenity" unless distributed to minors or exposed offensively to unconsenting adults. These disagreements among the Justices resulted in three different hearings, pushing Miller's case into 1973.

Since the Roth v. United States ruling in 1957, the Supreme Court had struggled to define what embodied constitutionally unprotected obscene material. Under the Comstock laws controlling mail distribution that prevailed before Roth, any material that tended to "deprave and corrupt those whose minds are open to such immoral influences" was deemed "obscene" and could be banned on that basis. Roth defined obscenity more strictly, as material whose "dominant theme taken as a whole appeals to the prurient interest" to the "average person, applying contemporary community standards". Only material meeting this test could now be banned as "obscene".

In Jacobellis v. Ohio in 1964, about a state ban of an adult-oriented film, Justice Potter Stewart opined that the Court "was faced with the task of trying to define what may be indefinable", and that criminal laws were constitutionally limited to hardcore pornography, which he did not try to define: "perhaps I could never succeed in intelligibly doing so. But I know it when I see it". In Memoirs v. Massachusetts in 1966, the Supreme Court refined the Roth test to material that is "patently offensive" and "utterly without redeeming social value". These precedents resulted in an unclear definition of obscene material that could be banned by government authorities.

Miller had based his appeal in California on the Memoirs v. Massachusetts precedent, particularly its test for material without any redeeming social value. Miller believed that such material had value for consenting adults who purchased it voluntarily. Per this argument positioning such material as items of expression, the question before the Court was whether the sale and distribution of that material was protected under the First Amendment's guarantee of freedom of speech. The court determined that the material at issue in Miller's case was pornography that could have been banned under the Roth precedent.

However, the Court acknowledged "the inherent dangers of undertaking to regulate any form of expression", and said that "State statutes designed to regulate obscene materials must be carefully limited." The Court, in an attempt to set such limits, devised a set of three criteria which must be met for a media item to be legitimately subjected to state regulatory bans:
199 whether the average person, applying contemporary community standards, would find that the work, taken as a whole, appeals to the prurient interest;
299 whether the work depicts or describes, in an offensive way, sexual conduct or excretory functions, as specifically defined by applicable state law; and
399 whether the work, taken as a whole, lacks serious literary, artistic, political, or scientific value.
This test clarified the definition of obscenity originally set out in the Memoirs precedent. This three-part analysis became known as the Miller test.

The result of the ruling was that the Supreme Court overturned Miller's criminal conviction and remanded the case back to the California Superior Court for reconsideration of whether Miller had committed a misdemeanor. On overturning Miller's conviction, the Court stated: "Under the holdings announced today, no one will be subject to prosecution for the sale or exposure of obscene materials unless these materials depict or describe patently offensive 'hard core' sexual conduct specifically defined by the regulating state law, as written or construed."

The Miller ruling, and particularly the resulting Miller test, was the Supreme Court's first comprehensive explication of obscene material that does not qualify for First Amendment protection and thus can be banned by governmental authorities. Furthermore, due to the three-part test's stringent requirements, very few types of content can now be completely banned, and material that is appropriate for consenting adults can only be partially restricted per delivery method.

The ruling had no direct impact on government attempts to restrict live adult entertainment, which is largely addressed in another Supreme Court precedent from roughly the same period: Paris Adult Theatre I v. Slaton.

Categories of media material that completely fail the Miller test, and thus can be completely banned by government authorities, have been narrowed down in later Supreme Court rulings. Child pornography was deemed to be unprotected by the First Amendment in New York v. Ferber in 1982, because it has no redeeming social value per the Miller test. In Ashcroft v. Free Speech Coalition in 2002, however, the Court held that sexually explicit material that only appears to depict minors, but actually does not, might be exempt from obscenity rulings.

The "community standards" portion of the Miller test is of particular relevance with the rise of the Internet, as materials believed by some to be "obscene" can be accessed from anywhere in the nation, including places where there is a greater concern than other areas of the nation. Enforcing and applying obscenity laws to the Internet have proven difficult. Due to the difficulty in determining which "community" is most relevant, both the Child Pornography Prevention Act (CPPA) and the Child Online Protection Act (COPA) have had sections struck down as unconstitutional in cases such as Ashcroft v. Free Speech Coalition and Ashcroft v. ACLU.