Is it true that no person is above the Law in the United States?

No person is above the Law in the United States. That's what we are taught as foundational to American principles. Our country is built upon that foundation.
In logic, the law of non-contradiction states that contradictory propositions cannot both be true in the same sense at the same time, e. g. the two propositions "A is B" and "A is not B" are mutually exclusive.

So you cannot be A, and be NOT A at the same time in the same context. OK?

Modus Ponens: The mode that affirms. If/then
P1. If it rained, then the streets are wet
P2. the streets are wet,
C: therefore; it rained.

Modus Tollens. The mode that denies. If/then
P1. If it rained, then the streets are wet
P2. the streets are dry
C: therefore; it did not rain

That's the logic.

Modus Ponens: If/then
P1. If the president can’t be indicted, then he is above the law
P2. the president cannot be indicted
C: therefore; he is above the law.

Modus Tollens: If/then
P1. If the president cannot be indicted, then he is above the law
P2. No one is above the law
C: therefore; the president can be indicted

If theory T is true, then we should observe O.
We do not observe O.
Therefore, theory T is false. ( Modus Tollens )

If P, Then Q.
Not Q
Therefore, Not P

Modus Tollens

That’s the logic.

So, apparently one person IS above the law. For AG Barr to suggest that the President cannot be indicted for obstruction of justice or any other crime is to make the claim that the President is above the law as demonstrated through Modus Ponens. Impeachment of the President does not guarantee that justice will be served, because of the tribal nature of our politics. If the president cannot be convicted in the Senate because of party loyalty, regardless of his crimes, then he can't be removed from office, and if he can't be removed from office, he cannot be indicted. Therefore, he is above the law. It simply cannot be applied to him. I don't think that's what the framers of the constitution had in mind. If no person is above the law, as demonstrated in Modus Tollens, then the policy set by the Office of Legal Council in the Department of Justice is standing on a logical contradiction in applying the law.

I am sure there are many legal responses to this (outside my domain of expertise) so I will simply address the logic. The problem is with the ambiguity of terms. What does "above the law" mean? If we define "above the law" as "cannot be indicted" then if it is the case that the president cannot be indicted then the president is "above the law."

P1. Someone is "above the law" if they cannot be indicted.
P2. The president of the US cannot be indicted.
C. Therefore, the president of the US is "above the law".

The (logical) debate would be around premise #1. Premise 2 could be debated by lawmakers.

Totally agree with Dr Bo.

I would also add that you accidentally Affirmed the Consequent in your wet pavement example.

Whether a sitting President can be indicted is definitely a legal question rather than a logical one. AG Barr is apparently of the opinion that they cannot. However, AG Barr also argues that you cannot commit obstruction of justice if there is no underlying crime. This is a bizarre assertion and puts him very much in the minority of the legal profession, and calls into question to what extent motivated reasoning and special pleading are driving his public utterances in this case. Certainly Robert Mueller indicated very strongly in his report that the Congressional solution (ie impeachment) was the way to deal with these crimes.

As to whether tribal politics puts Trump above the law? I'm not sure we can say that. Yes, it means he is significantly more likely to be acquitted by the Senate if the House chose to impeach, but then in a regular court attractive people are less likely to be found guilty than unattractive people ( www.psychologytoday.com/g. . . Does that mean unattractive people are 'above the law', or does it just mean the system of justice has some inherent flaws?

It should be noted that Mueller states, and I believe Barr agrees that once a president is removed from office they most certainly can be indicted. So this would have to amend to The President is only temporarily above the law. This might also apply to other statutes of limitation as well, such as in many crimes a person may be above the law after a certain amount of time.

Another consideration is that the House could impeach the president entirely on its own and not submit it to the senate. This is known as the Tribe solution.

https://www.google.com/amp/s/beta.washingtonpost.com/opinions/impeach-trump-but-dont-necessarily-try-him-in-the-senate/2019/06/05/22d83672-87bc-11e9-a870-b9c411dc4312_story.html%3FoutputType%3Damp

I see several logical issues here. First argument:

P1. If the president can’t be indicted, then he is above the law
P2. the president cannot be indicted
C: therefore; he is above the law.

P1 is incorrect; others have pointed out, and Mueller stated in his report, that a sitting President can certainly be indicted after he leaves office. Therefore, he cannot be indicted while he is President , but he is not above the law.
This leads nicely into the second predicate. P2 is not strictly true. The president can be indicted; there are no laws forbidding it. All that is preventing it is Department of Justice policy.
So we have two predicates that are not always true. Any conclusion is meaningless.

Second argument:

P1. If the president cannot be indicted, then he is above the law
P2. No one is above the law
C: therefore; the president can be indicted

Even though, according to our legal system, P2 is true, per the previous discussion, P1 is not true. Therefore, the conclusion does not follow.

As other people have stated, the argument boils down to definitions of "cannot be indicted" (while he is President, or ever?), and "above the law." There are things that the president can do by virtue of his position that others cannot legally do. Obstruction of justice is not one of them.

Indictment is the purpose of impeachment, and any president can be so indicted. Thus the original question is moot, nugatory.

The DOJ "policy" language, as I understand it, is to prevent every half-baked DA with a rubber stamp embossed "INDICTED" from putting the sitting president under perpetual kangaroo-court trials, though the MSM seems to have no trouble making up their own version - even to medical/psychological diagnosis - when it suits them (and so long as they get the Nielsen Ratings). I think it's exactly in keeping with the framers' intentions, just as the average citizen can't sue the government.

It is a bit amusing to see the disappointed TDS folks, here and elsewhere, trying, despite the (lack of) evidence, to indict or impeach Mr. Trump for the "high crime" of winning the Electoral College and the Presidency, but somehow ignoring the elephantette in the room whose obvious criminal negligence was imaginatively excused by James Comey, as "unintentional", when intention was not dispositive, coming as close as possible to doing the very thing Mueller could never have done properly, by law, "exonerating". Indeed, by his language, he found her guilty and pardoned her.

So I impeach my own first comment. The question is not nugatory, just misapplied. There appears to be at least one person above the law, though Hillary Clinton did not win the election.

I'd thank God, but I don't want to start an argument.