Would it be possible for the Supreme Court of the United States to void a Presidential Pardon? If so how would they do it? If not why?
No, the Judicial Branch has no power over Presidential Pardons, which are vested solely within that office.
The President is granted this power in Article 2. Section 2.
The President shall be Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States, when called into the actual Service of the United States; he may require the Opinion, in writing, of the principal Officer in each of the executive Departments, upon any Subject relating to the Duties of their respective Offices, and he shall have Power to grant Reprieves and Pardons for Offences against the United States, except in Cases of Impeachment.
Bradford v. Cardoza lays out the reasons.
Article II, section 2, clause 1 of the United States Constitution reads: "[The President] shall have power to grant reprieves and pardons for offenses against the United States, except in cases of impeachment." The draftsmen of this article intended it to be free of legislative control. (Schick v. Reed (1974) 419 U.S. 256, 263 [42 L.Ed.2d 430, 437, 95 S.Ct. 379], reh. den. 420 U.S. 939 [43 L.Ed.2d 416, 95 S.Ct. 1150].) [T]he pardoning power is an enumerated power of the Constitution and ... its limitations, if any, must be found in the Constitution itself." (Id., at p. 267 [42 L.Ed.2d at p. 439].) Congress therefore cannot modify, abridge or limit the President's pardon power.
“An unconstitutional act is not a law; it confers no rights; it imposes no duties; it affords no protection; it creates no office; it is in legal contemplation as inoperative as though it had never been passed.” Norton v. Shelby County, 118 U.S. 425 (1886)
“At the time of the adoption of the Federal Constitution, American statesmen were most familiar with the prerogatives exercised by the king, so that obviously when the words "to grant pardons" were used in the Constitution of the United States, they conveyed to mind the authority as exercised by the English crown.Hence, it may be truly stated that we adopted their principles respecting the operation and effect of a pardon, and relied on the early writings of the common law for rules prescribing the manner in which it is to be employed.”
“In the Constitution of the United States, and in most of the state constitutions, the pardoning power is there, in express, general terms, and by construction, since the greater includes the lesser power, it may be either absolute or conditional. This is true also in England. The pardoning executive may annex to his offer of pardon, then, any conditions that he may see fit to impose, either precedent, or subsequent. The only restriction upon this exercise of authority is that the condition must not be impossible of fulfillment, criminal or illegal in nature.“
Emphasis added See United States v. Six Lots of Ground, 27 Fed. Cas. No. 16,299, at 1098 (C. C. La. 1872), aff'd, 91 U. S. 21 (1875); Kavalin v. White, 44 F. (2d) 49, 51 (C. C. A. 10th, 1930); Ex parte Prout, 12 Idaho 494, 498, 86 Pac. 275, 276 (1906); 1 Bishop, NEW CRIMINAL LAW (8th ed. 1892) § 915.
With reference to illegal, immoral or impossible conditions, it has been stated that
"If the condition is of a sort not permissible, it is void, and the pardon is absolute." I Bishop, NEW CRIMINAL LAW (9th ed. 1923) 659.*** [Emphasis added] But, it seems clear that by declaring a condition precedent void, no such result should follow. See Canadian Prisoner's Case, 5 M. & W. 32, 49, 151 Eng. Reprints 15, 22 (1839) (if the condition upon which alone the pardon was granted be void, the pardon must also be void). That it should become absolute in the case of a void condition subsequent is supported by some authority. Taylor v. State, 41 Tex. Cr. R. 148, 51 S. W. 1106 (1899) (a pardon in which the governor reserved the right of revocation if the grantee violated any of the criminal laws of the state, held, condition void, pardon absolute); People v. Pease, 3 Johns. 333 (N. Y. 1803) (a proviso that a pardon was not to relieve the grantee of legal disabilities arising from his conviction, held, condition void, pardon absolute). Such decisions apparently rest upon a conception of pardons as of the nature of contracts or deeds. But the modern tendency is to regard them as acts in the interest of public welfare, wholly independent of the will of the prisoner. See Biddle v. Perovich, 274 U. S. 480, 486 (1927). To construe any expressly conditioned pardon as absolute is a perversion of the intent of the executive and creates an uncontemplated danger to the public. The alternative of holding it invalid leaves it open to the executive to grant a new absolute, or properly conditioned pardon as he sees fit.”
Hence, pardons granted as part of an illegal scheme to commit a crime like, Obstruction of Justice (to procure the silence or favorable false testimony of a witness), or Defrauding the United States (to conspire with as hostile foreign government to affect an federal election), or etc. would be void and unenforceable in court.
Hence, such pardons could not be relied upon to secure release from otherwise lawfully imposed punishment.
For example, if President Trump grants his family members or Mr. Manafort a pardon for purposes of a conspiracy to coverup a crime, such pardons are void and worthless.