The Constitution rules out immunity for sitting presidents

Here are the relevant sections of the Constitution:

I.2 The House of Representatives shall chuse their Speaker and other Officers; and shall have the sole Power of Impeachment.

I.3 The Senate shall have the sole Power to try all Impeachments. When sitting for that Purpose, they shall be on Oath or Affirmation. When the President of the United States is tried, the Chief Justice shall preside: And no Person shall be convicted without the Concurrence of two thirds of the Members present.

Judgment in Cases of Impeachment shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States: but the Party convicted shall nevertheless be liable and subject to Indictment, Trial, Judgment and Punishment, according to Law.

I.6 [The Senators and Representatives] shall in all Cases, except Treason, Felony and Breach of the Peace, be privileged from Arrest during their Attendance at the Session of their respective Houses, and in going to and returning from the same; and for any Speech or Debate in either House, they shall not be questioned in any other Place.

II.1 The executive Power shall be vested in a President of the United States of America.

II.2 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 ...

II.2 ... and he shall have Power to Grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment.

II.2 He shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur; and he shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, other public Ministers and Consuls, Judges of the supreme Court, and all other Officers of the United States, whose Appointments are not herein otherwise provided for, and which shall be established by Law: but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments.

II.4 The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors.

III.2 The Trial of all Crimes, except in Cases of Impeachment, shall be by Jury ...

III.3 Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.

VI.1 This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.

Amendment 25
4. Whenever the Vice President and a majority of either the principal officers of the executive departments or of such other body as Congress may by law provide, transmit to the President pro tempore of the Senate and the Speaker of the House of Representatives their written declaration that the President is unable to discharge the powers and duties of his office, the Vice President shall immediately assume the powers and duties of the office as Acting President.

Thereafter, when the President transmits to the President pro tempore of the Senate and the Speaker of the House of Representatives his written declaration that no inability exists, he shall resume the powers and duties of his office unless the Vice President and a majority of either the principal officers of the executive department or of such other body as Congress may by law provide, transmit within four days to the President pro tempore of the Senate and the Speaker of the House of Representatives their written declaration that the President is unable to discharge the powers and duties of his office. Thereupon Congress shall decide the issue, assembling within forty eight hours for that purpose if not in session. If the Congress, within twenty one days after receipt of the latter written declaration, or, if Congress is not in session, within twenty one days after Congress is required to assemble, determines by two thirds vote of both Houses that the President is unable to discharge the powers and duties of his office, the Vice President shall continue to discharge the same as Acting President; otherwise, the President shall resume the powers and duties of his office.

So Article II, section 2 makes it impossible for the former VP to pardon a former president who was removed by impeachment, at least for crimes for which he was impeached, and arguably for any crime, whether or not a conviction was obtained in the Senate. 

While admitting that the Constitution lays out clearly impeachment is the only means by which a president may be removed from office, and specifically states that after being removed from office he may be indicted and charged for crimes, Tribe says that it must be that the Constitution also allows presidents to be tried for crimes because otherwise the president might conspire with the vice president to pardon him, thus escaping punishment.

Tribe states that the Justice Department has always had a policy of not prosecuting a sitting president based on the obvious language of the impeachment clause but he says this is wrong and unconstitutional.

https://www.bostonglobe.com/opinion/2018/12/10/constitution-rules-out-sitting-president-immunity-from-criminal-prosecution/6Byq7Qw6TeJlPVUhlgABPM/story.html

Tribe's claim is that he interprets the Constitution better than 229 years of precedent.

 If the VP conspires with the president, the Constitution provides a clear remedy: namely impeaching the VP. As a practical matter, this will be easy because it will occur according to his argument in a context where the president has already been impeached meaning the Congress is politically against his party.

 The founders were justly and rightly concerned about rogue prosecutors and political prosecutions of the president. Thus they made clear these were not allowed in the impeachment clause.

 Right now it is apparent that the deep state is  much of the way to taking over the government. We are living in a country where the CIA spied on the Senate, Brennan, the CIA director, lied under oath about this to the Senate, and then was forced to admit he had lied, and he wasn't even fired, much less prosecuted for perjury or sedition! Then, two years after the election  the controlled media screamed when his security clearance was lifted!  Moreover the deep state even according to Comey's testimony launched an investigation of Trump's campaign including investigating former members of it and surveilling them with no evidence that he can recall. Moreover they didn't prosecute his opponent, although it's  undisputed that she had her emails deleted after receiving a subpoena for them. https://www.theepochtimes.com/key-takeaways-from-james-comeys-testimony-before-congress_2734427.html  There is a clear and present danger that a rogue prosecutor will end our democracy.

 If the president were pardoned for actual crimes and escaped justice, why would Tribe conclude that was a worse scenario in the eyes of the authors of the Constitution than rogue prosecutors? Rogue prosecutors damage the country And are close to ending our democracy.

The Justice Department has always had a policy of not prosecuting sitting presidents on the grounds that the Constitution lays out that they should be instead impeached.

 This policy is unconstitutional.