Article 1, section 3:
I think we have to look at the totality of impeachment as addressed in the Constitution:
Article 1, section 2:
...
The House of Representatives shall chuse their Speaker and other Officers; and shall have the sole Power of Impeachment.
Impeachment is thus mentioned, but not defined.
Article 1, section 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.
Again, impeachment is mentioned but not defined. So we still don't know who can be impeached, except that the list includes (but is apparently not limited to) the President.
Words have meaning, and in law words have very specific meanings. My work for the past 30+ years has been code enforcement, and for all those thirty years the people teaching our in-service classes have stressed that "and" does not include "or." If a law calls for something if 'A'
and 'B' are met, then both 'A' and 'B'
must be present or the condition does not apply. If a law calls for something if 'A'
or 'B' is met, then the law applies if either 'A' or 'B' or both is/are present.
What the Constitution says is that the punishment upon conviction by the Senate "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." Therefore taken at face value based on the language of the Constitution and the principles under which all laws are construed, since Trump is no longer in office he cannot be removed from office "and" prohibited from holding federal office again. Therefore, my opinion (as a linguist, not a self-proclaimed Constitutional scholar like a certain former President) is that the trial has no merit and is not constitutional.
Now lets look at where else impeachment is mention in that musty old Constitution.
Article 2, Section 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.
And there you have it. Article 2 is "The Executive Branch," and Section 4 is "Disqualification." It says the President, Vice President, and all civil officers may be removed from office upon impeachment and conviction. Article 1 IMHO only establishes who has the authority to do the impeaching. Article 2 Section 4 establishes who can be impeached, and it includes only current office holders. Right now, and as of 20 January, Donald Trump is a private citizen, not an officer of the United States government. The government's authority to impeach him ended the moment he left office. He can be prosecuted in criminal court and/or sued in civil court, if they think they have a case, but (IMHO) he cannot now be tried by the Senate and convicted.