Can a U.S. President undo an act of clemency or a pardon of his predecessor? Can the next U.S. President undo the current President's pardons?
No. There are few if any checks on any President for any Pardons issued (a general Impeachment may be the only check but there has never been a strong call for impeachment for a pardon.). Further more, the protection against Double Jeopardy is in effect meaning future Presidents cannot prosecute the pardon recipient for any crimes that were pardoned by a previous president, though they may prosecute any future criminal incidents perpetrated by the pardoned person that are not related to the events surrounding the pardoned crime.
The judge's decision is reversed or vacated, and then she continues being a judge as though nothing happened. There are essentially no consequences available for federal judges, with the exception of impeachment.
How would this scenario play out in the legal system? Prosecutor brings charges against EQM or tries to use that conviction to enhance a subsequent conviction. Defendant EQM raises the pardon as a defense. Prosecutor responds that the pardon was intended to cover EQM Prime, not EQM. The Court holds an evidentiary hearing to determine whether the President intended to pardon EQM Prime or EQM. The Court decides who the President intended to pardon based upon the evidence presented at the hearing, and rules accordingly. The burdens of proof are tricky. Usually affirmative defenses have a preponderance of the evidence burden on the proponent of the defense, but sometimes the defense must be disproved beyond a reasonable doubt. I don't know that part of the law well enough to know without lots of research and the outcome might not be uniform across the U.S. To my knowledge, there has never been a case that got this far in which the true identity of the beneficiary of the pardon was ambiguous. It is possible, but a vanishingly rare possibility. Almost always, someone gets a pardon by asking for it and determining whether EQM or EQM Prime asked resolves it, or a reference to the crime resolves it. If the Court concludes that both asked the same President to be pardoned for the same crime (e.g. if the same crime was committed jointly by father and by son who is named after father and doesn't use Jr. day to day) and the Court concludes that the President was probably confused and didn't realize that there were two requests from different people and not one, the judge would probably give them the benefit of the doubt and treat both as pardoned as that would still reflect the President's intent.
Let's start with the most important point first: A campaign finance violation is not a ground to remove an elected official from office, no matter how egregious, on its own, even if one could prove that the campaign finance violation probably caused the outcome of an election to change. Congress could decide, however, that a campaign finance violation constitutes a "high crime or misdemeanor" for which a sitting President could be impeached, if a majority of the House of Representatives votes to impeach the President and a two-thirds majority of the U.S. Senate trying the impeachment under the supervision of the Chief Justice of the United States (that and not "Chief Justice of the United States Supreme Court" is the official title) finds that the offense set forth in the impeachment has been committed and constitutes sufficient grounds to remove the President from office. At the outset, there is some ambiguity over whether the violation of campaign finance laws would have been by individual person, or the political campaign of the individual person (which is a Section 529 non-profit organization). The individual or the campaign, as the case might be, would definitely owe either civil or criminal fines, as the case might be, for a violation of the particular campaign finance laws that the individual or campaign is alleged to have violated. The violation could also affect the ability of the violator to obtain all or any amount of federal matching funds in a future election. Depending upon the particular campaign finance law involved, which isn't clearly specified, there might be a criminal penalty (either a misdemeanor or a minor felony) as well, which could give rise to a probation sentence, a sentence to some period of incarceration, a period of post-release parole, criminal fines, court costs, and, at least in the case of a felony, some collateral consequences of that conviction such as a prohibition on owning a gun and ineligibility for many occupations and jobs. Neither a civil campaign finance violation, nor a criminal conviction for a campaign finance violation, disqualifies someone from holding the office of President. The President does not have immunity from civil or criminal consequences of campaign finance violations committed prior to taking office, and the President's campaign, at a minimum, is not immune to campaign finance violations at any time. Presidential immunity from liability is limited to the conduct of the President while holding the office in furtherance of the governance duties of the President. Generally speaking, campaigning would not be a governance duty of the President, but there are factual circumstances under which it is hard to distinguish between what constitutes governing and what constitutes campaigning in the case of a sitting President who is currently in office. Also, campaign finance violations can't be prosecuted by just anyone. A violation of federal campaign finance laws must be prosecuted by a federal government lawyer authorized to do so by the Federal Election Commission (FEC), which has an even partisan balance of members by design and almost always deadlocks on motions to prosecute anything but the least controversial and most blatant campaign finance violations against members of either of the two major political parties in the United States. A "private attorney general" can't bring a lawsuit to enforce campaign finance laws unilaterally. The President can definitely pardon a criminal violation of a campaign finance law by anyone other than himself. The President definitely cannot pardon a civil violation of a campaign finance law by anyone. The majority and more analytically sound position is that the President cannot pardon himself for his own criminal violation of a campaign finance law (there are prior questions and answer at Law.SE regarding that question). A judge considering a campaign finance violation charge against a sitting President could, however, take steps short of dismissing the charges that could accommodate a sitting President. For example, the judge could be very deferential to the President in setting hearing dates, allowing the President to participate in proceedings by telephone or (in some but not all cases) through a representative, or in setting the amount of a bond or the terms of pre-trial release in the event of a criminal charge, or in cooperating with the President's security detail when the President is required to appear. In a civil violation case, the President would probably be allowed to be a deposition witness, with the deposition testimony used at trial, rather than appearing in person at trial, if his lawyers requested that treatment.
The canonical example is Gerald Ford's pardon of Richard Nixon.
In general, no, if you make a will then you can revoke that will while ever you are still legally competent. Also, in general, this is a good thing. For your first example, you are ruling out all possibility of redemption - people change: a person who is a selfish a*$%^#@e in their 20s may be a kind, caring, dutiful and loving person in their 40s. For your second example, what if XXX gets demolished? Or you move cities? If you are truly serious, you can transfer all your assets to a trust, put your instructions in the trust deed and then nominate someone you really, really, really trust to be the trustee. This would prevent you modifying the instructions but you are then relying on the trustee interpreting them.
Yes, the President can just fire them, or more commonly, request their resignation. The provision for impeachment by Congress exists in case the President doesn’t do what the President should do.
Not for that reason This would not make the Act invalid. The interaction between the two laws would simply mean that criminal prosecution would only succeed for acts on or after the Act came into effect. So, even though the law purports to invoke criminal sanction for acts before it came into effect, the Constitution says it can’t so it doesn’t. That doesn’t render the law invalid, just unenforceable for that period.