As most are aware now, a Federal Judge ruled that Don McGahn must appear before Congress to testify, when compelled to do so. The balance of powers spelled out in the Constitution, demand this compliance. And the arguments put forward by the Trump Attorneys, forcing witnesses to remain silent — are basically bunk.
Sincerely hat-tip to Rachel Maddow, for putting some of these stunning statements buried in the fine print of the Judge’s ruling, on my radar screen. Here’s are a few of those legal rationales (pdf) that she highlighted in her show, plus a few others for good measure:
Stated simply, the primary takeaway from the past 250 years of recorded American history is that Presidents are not kings.
— pg 114
This means that they do not have subjects, bound by loyalty or blood, whose destiny they are entitled to control. Rather, in this land of liberty, it is indisputable that current and former employees of the White House work for the People of the United States, and that they take an oath to protect and defend the Constitution of the United States.
— pg 114
Moreover, as citizens of the United States, current and former senior-level presidential aides have constitutional rights, including the right to free speech, and they retain these rights even after they have transitioned back into private life.
— pg 114
To make the point as plain as possible, it is clear to this Court for the reasons explained above that, with respect to senior-level presidential aides, absolute immunity from compelled congressional process simply does not exist.
— pg 115
Indeed, absolute testimonial immunity for senior-level White House aides appears to be a fiction that has been fastidiously maintained over time through the force of sheer repetition in OLC opinions, and through accommodations that have permitted its proponents to avoid having the proposition tested in the crucible of litigation.
— pg 115
[T]he contention that a President’s top advisors cannot be subjected to compulsory congressional process simply has no basis in the law […]
— pg 115
Thus, for the myriad reasons laid out above as well as those that are articulated plainly in the prior precedents of the Supreme Court, the D.C. Circuit, and the U.S. District Court for the District of Columbia, this Court holds that individuals who have been subpoenaed for testimony by an authorized committee of Congress must appear for testimony in response to that subpoena—i.e., they cannot ignore or defy congressional compulsory process, by order of the President or otherwise.
— pg 116
And when deconstructing Bill Barr’s assertions of unitary executive power to protect Trump for anything he does — Judge Jackson bluntly compares Barr’s reasoning to that of George Orwell’s Animal Farm, in Footnote 11:
Meanwhile, says DOJ, the President has the authority to make unilateral determinations regarding whether he and his senior-level aides (both current and former) will respond to, or defy, the subpoenas that authorized House committees issue during constitutionally authorized investigations of potential wrongdoing within his administration. […] 
 For a similar vantagepoint, see the circumstances described by George Orwell in the acclaimed book Animal Farm. See George Orwell, Animal Farm 141 (Otbe Book Publishing 2018) (“All animals are equal but some animals are more equal than others.”) (capitalization altered).
— pg 38-39
With the zoo of Trump’s many many abuses of power — strongly assisted by his personal interference Attorney Bill Barr, to fend off all Constitutional defenders — perhaps a more apt comparison would be hard to find.