Below are the basic legals defining Treason

To my understanding only Congress can impeach the President. However, any one can sue any one - treason or other criminal acts against the Constitution and lessor crimes. 

Presidental Oath of Office

In the United States, the oath of office for the President of the United States is specified in the U.S. Constitution (Article II, Section 1): Article II, Section I of the U.S. Constitution:

I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States.

The oath may be sworn or affirmed. Although not present in the text of the Constitution, it has been conventional for Presidents to add "so help me God" at the end of the oath. George Washington did this at his inauguration in 1789. [1]

TREASON by a PRESIDENT

Constitution of the United States : Article II, Section 4
All civil offices forfeited for certain crimes.
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.

The Constitution specifies in Article VI, clause 3:
TITLE 5 > PART III > Subpart B > CHAPTER 33 > SUBCHAPTER II > § 3331

"The Senators and Representatives before mentioned, and the members of the several state legislatures, and all executive and judicial officers, both of the United States and of the several states, shall be bound by oath or affirmation, to support this Constitution; but no religious test shall ever be required as a qualification to any office or public trust under the United States."

For other officials, including members of Congress, it specifies they "shall be bound by Oath or Affirmation to support this constitution." At the start of each new U.S. Congress, in January of every odd-numbered year, those newly elected or re-elected Congressmen - the entire House of Representatives and one-third of the Senate - must recite an oath:

I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter: So help me God.

This oath is also taken by the Vice President, members of the Cabinet, and all other civil and military officers and federal employees other than the President. (Military personel have a separate Oath - their Orders are from the Commander in Chief - the President)

TREASON by a Congressman

Constitution of the United States : Article II, Section 4
All civil offices forfeited for certain crimes.
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.

Judges Oath of Office

The Judiciary Act of 1789, which established an additional oath taken by Supreme Court justices and district court judges:

I do solemnly swear (or affirm), that I will administer justice without respect to persons, and do equal right to the poor and to the rich, and that I will faithfully and impartially discharge and perform all the duties incumbent on me, according to the best of my abilities and understanding, agreeably to the Constitution, and laws of the United States. So help me God.

TREASON by a Judge

Constitution of the United States : Article II, Section 4
All civil offices forfeited for certain crimes.
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.

Any Judge that is not fully compliant Constitutionally orders are void, without jurisdiction, and are acts of treason. 124. U.S. 200 (1888)

The 14th Amendment, states that Federal law is applicable to all States.

Here are some Supreme Court reference cases:

The consistant rulings by the Supreme Court says any Judge that acts in violation of their Oath wars against the Constitution, and engages in acts of treason.

Elliot v. Piersol, 1 Pet. 328, 340,26 U.S. 328, 340 (1828)
Cooper v. Aaron, 358 U.S. 1, 78 S.Ct. 1401 (1958)
Scheuer v. Rhodes, 416 U.S. 232, 94 S.Ct. 1683, 1687 (1974)