The first portion of the brief sets forth the background of the invention, the patent, the litigation, and both Federal Circuit panel (1 and 2) and en banc opinions (the latter deciding not to rehear the case en banc).  In summary, a divided panel (Judges Dyk and Taranto) affirmed the District Court's summary judgment decision that the claims below are ineligible for patenting under the Supreme Court's decisions in Mayo Collaborative Servs. v. Prometheus Labs., Inc. and Alice Corp. Pty. Ltd. v. CLS Bank International.

1.  A method for manufacturing a shaft assembly of a driveline system, the driveline system further including a first driveline component and a second driveline component, the shaft assembly being adapted to transmit torque between the first driveline component and the second driveline component, the method comprising:
    providing a hollow shaft member;
    tuning at least one liner to attenuate at least two types of vibration transmitted through the shaft member; and
    positioning the at least one liner within the shaft member such that the at least one liner is configured to damp shell mode vibrations in the shaft member by an amount that is greater than or equal to about 2%, and the at least one liner is also configured to damp bending mode vibrations in the shaft member, the at least one liner being tuned to within about ±20% of a bending mode natural frequency of the shaft assembly as installed in the driveline system.

22.  A method for manufacturing a shaft assembly of a driveline system, the driveline system further including a first driveline component and a second driveline component, the shaft assembly being adapted to transmit torque between the first driveline component and the second driveline component, the method comprising:
    providing a hollow shaft member;
    tuning a mass and a stiffness of at least one liner, and
    inserting the at least one liner into the shaft member;
    wherein the at least one liner is a tuned resistive absorber for attenuating shell mode vibrations and
    wherein the at least one liner is a tuned reactive absorber for attenuating bending mode vibrations.

The majority's rationale, which the Solicitor General argues was erroneous, was based on the claims reciting nothing more than a "natural law" (Hooke's Law), despite this physics concept appearing nowhere in the claims.  Judge Moore strongly dissented in both the original panel decisions and the decision not to rehear the matter en banc.

The Solicitor General's brief is directed to the first of the Questions Presented:

Section 101 of the Patent Act of 1952, 35 U.S.C. 1 et seq., provides that "any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof," is eligible for a patent.  35 U.S.C. 101.  The questions presented are as follows:

1.  Whether claim 22 of petitioner's patent, which claims a process for manufacturing an automobile driveshaft that simultaneously reduces two types of driveshaft vibration, is patent-eligible under Section 101.

2.  Whether patent-eligibility under Section 101 is a question of law for the court based on the scope of the claims or a question of fact for the jury based on the state of the art at the time of the patent.

The Solicitor General's (SG) argument is based on traditional concepts of patent-eligible subject matter.  The SG states that "[h]istorically, [later specified as "for more that 150 years"] such industrial techniques have long been viewed as paradigmatic examples of the 'arts' or 'processes' that may receive patent protection if other statutory criteria are satisfied."

The brief states in several places that it is the Mayo/Alice framework itself that has "given rise to substantial uncertainty."  It is perhaps a not-so-subtle signal that the SG's brief cites for many of these historical principles the Court's decision in Diamond v. Diehr, perhaps signaling to the Court that in making its rhetorical choice in Mayo, the Court would have been better served to follow Diehr rather than Parker v. Flook, which was decided earlier.  The SG's brief sets forth four "relevant considerations" that "supply useful guideposts" in properly applying the Mayo/Alice test.  These are:

First, a fundamental distinction between patents that "claim the 'building blocks' of human ingenuity" and those that "integrate the building blocks into something more," and "thereby 'transforming' them into a patent-eligible invention."  The brief characterizes the purpose of the test to "distinguish between those two types of claimed inventions."  The brief cites again Diehr to be illustrative of the difference between patent-eligible and -ineligible claims.

Second, that the Court has equally recognized that "[a]t some level, 'all inventions . . . embody, use, reflect, rest upon, or apply laws of nature, natural phenomena, or abstract ideas,' " citing (ultimately) Mayo, and that this recognition produced on the Court an obligation to "tread carefully in construing th[e] exclusionary principle lest it swallow all of patent law," and that "an invention is not rendered ineligible for patent simply because it involves" a patent-ineligible concept, citing Diehr and providing as an example Eibel Process Co. v. Minnesota & Ontario Paper Co., 261 U.S. 45, 52-69 (1923).

Third, the SG implicates the importance (and restrictions) that "the Section 101 inquiry is guided by historical practice and judicial precedent," citing Bilski v. Kappos, 561 U.S. 593 (2010), for this reliance (and obligation) on history.  These obligations are particularly relevant here, according to the SG, because "[c]ourts thus should be skeptical of any assertion that a claim for the sort of process that has long been held patent-eligible, such as an industrial manufacturing process, is unpatentable under the 'law of nature' exception."

Finally, the SG raises the Court's concern regarding preemption (as a justification for the exclusionary exceptions with regard to the constitutional limitations of Congress's power to grant patents).

The SG advocates that the Federal Circuit erred in the applications of these principles, in particular comparing American Axle's claims and the claims in Mayo and Alice.  In the SG's view, the claims at issue here are an application of natural law (such as Hooke's law) that are eligible "because all useful inventions that operate in the physical world depend for their efficacy on natural laws (whether known or unknown), such dependence by itself cannot render claim 22 patent-ineligible" (the SG making explicit favorable comparisons again with the claims in Diehr).  The SG in similar fashion sees the claims here to be consistent with the Supreme Court's eligibility principles as illustrated herein.

The SG also distinguishes Claim 22 here from Claim 8 in Morse's patent invalidated by the Court in O'Reilly v. Morse, 56 U.S. (15 How.) 62 (1854).  The SG's basis for this distinction is that Claim 22 does not merely recite a "goal" (analogous to Morse's claim) but rather "recites a specific sequence of steps to achieve that goal."  The brief makes an important argument regarding the panel majority's reasoning in this regard, saying that the majority committed fundamental error in its "premise that conventional claim elements could be disregarded at step two of the Mayo/Alice test."  And the SG traces that error to the language in both Mayo and Alice that "a claim must include more than steps or elements that are 'well-understood, routine, conventional activities' in the relevant field."  But the SG apprehends that the Court "did not intend to endorse a categorical rule that conventional claim elements should be disregarded in determining whether particular claims reflect an " inventive concept, " or "add enough" to natural laws or phenomena, so as to warrant patent protection."  The basis for this apprehension is that the Court "did not question the long-settled understanding that the patent eligibility of a process claim turns on 'the process as a whole, and that 'an application of a law of nature or mathematical formula' may be patent-eligible even if the law or formula is applied 'to a known structure or process,'" again citing Diehr.

And this question is "especially important" according to the SG because its answer is relied upon in addressing the second step of the Mayo/Alice test.  In view of this importance, the SG states that "the step-two analysis should be performed in accordance with the longstanding principle that a combination of claim elements may reflect a patent-eligible invention even though each individual element was part of the prior art" (emphasis added).  The SG suggests that what cannot happen is for a court to be foreclosed in step two of the Mayo/Alice test from considering claim elements that have "traditionally been viewed as relevant to patent-eligibility" (because they are "routine, conventional, and well-understood," for example), then those considerations would need to be "incorporated in some fashion into the step-one inquiry."

The SG also takes the opportunity to review the somewhat bedraggled ("fractured") state of eligibility jurisprudence at the Federal Circuit, citing specifically Athena Diagnostics, Inc. v. Mayo Collaborative Servs., LLC, 915 F.3d 743 (Fed. Cir. 2019), and Ariosa Diagnostics, Inc. v. Sequenom, Inc., 788 F.3d 1371 (Fed. Cir. 2015) (and noting in each instance that rehearing was denied).  This "ongoing uncertainty" has caused "every judge" on the Federal Circuit to ask for Supreme Court clarification of the standard (citing Judge Moore's dissent below).  The SG also notes and calls out the particular problems that have arisen regarding the proper scope of eligibility in fields such as medical diagnostics (again citing Judge Moore).  But, the SG notes, the problem of "inconsistency and unpredictability of adjudication" extend to "all fields," citing Judge Newman's dissent in Yu v. Apple Inc., 1 F.4th 1040, 1049 (Fed. Cir. 2021), and Chamberlain Grp., Inc. v. Techtronic Indus. Co., 935 F.3d 1341, 1348 (Fed. Cir. 2019).  Also garnering mention is the commentary accompanying the 2019 Guidance on Subject Matter Eligibility at the USPTO, which asserted that interpreting the Supreme Court's and Federal Circuit's jurisprudence on subject matter eligibility has been "in a consistent manner has proven to be difficult"; "has caused uncertainty in this area of the law"; has made it difficult for "inventors, businesses, and other patent stakeholders to reliably and predictably determine what subject matter is patent eligible"; and "poses unique challenges for the USPTO" itself.

The brief concludes with the SG's opinion that this case is a suitable vehicle for the Court to provide the requested "greater clarity," and rebuts each of Respondent's reasons why the Court should not grant certiorari.  As for the second of the Questions Presented, the SG states that the Court must clarify eligibility by addressing the first Question because the procedural answer to the Second ("satellite") Question depends on the Court's answer to the first.

Whether due to the change of administrations, or the mounting number of certiorari petition denials on subject matter eligibility, or the facial egregiousness of finding claims to methods for reducing vibration in a truck axle ineligible as being nothing more than a natural law, the SG's brief raises the possibility that the Court will reduce if not refute some of the more worrisome extensions by lower courts of its Mayo/Alice precedent.  While Respondents and others have urged the Court to consider eligibility cases from the life sciences or computer technologies, it is perhaps better for a simpler technology to be the basis for the Court's reconsideration, in the same way that patent practitioners just starting out learn their craft by drafting simple mechanical claims.  Without the distraction of the technology, perhaps, the foundational principles that patent laws have traditionally relied upon may become easier to discern and produce a more consistent, reliable test that has fewer anomalous results and that restores the ability to patent American innovation in important technological areas.  A patent practitioner can dream, after all.