He pointed to the power of Congress to hold a president to account – an argument that will reflect Trump's attempt to fend off an oversight offensive.
Trump appeals to the ruling and threatens long legal disputes – Monday's decision was a setback in a much longer war, a factor that gave Trump a significant political advantage.
As a rule, his response signaled that he has no intention of backtracking, and will take up any fight in his fight against him, possibly Congress, as far as he can, before the Supreme Court.
But Monday set an early milestone in the feud of separation of powers between Congress and the White House and could indicate how other legal disputes between Democrats and Trump could be pan out.
"It is a good opinion, and it provides a very good framework for the way in which all the disputes between the House committees and the White House are going on," said Preet Bharara, former US attorney for the South District of N ew York said on CNN "Anderson Cooper 360".
Depending on how the White House responds to possible court decisions that contradict the wishes of the President, Monday's drama may have brought a constitutional crisis one step closer.
Former James Baker, FBI's General Counsel, said to CNN's Wolf Blitzer on Monday that Congress had not always exercised the powers of the Mazars case and had relinquished power to the presidency over the years.
"I think it's a recognition that Congress has a lot of power under the Constitution ̵
Trump's legal team had argued that Congress is on a crusade to overturn material that the Democrats could use to embarrass him now and in the 2020 presidential election.
But the chairman of House Oversight, Elijah Cummings, a Democrat from Maryland, called the ruling a "sweeping victory for the rule of law and our constitutional system of control and balance". 
Democrats did not make it all the way on Monday
And McGahn confirmed that he would not turn up for a hearing of the House Judiciary Committee on Tuesday, which is sure to turn into a theater performance in front of an empty witness chair. Emagazine.credit-suisse.com/app/art … = 157 & lang = DE His lawyer, William A. Burck, argued that McGahn was subject to contradictory instructions from two equal – ranking branches. But the New York Democrat Jerry Nadler , Justice Leader, told reporters: "We have tomorrow's hearing and expect Mr. McGahn to appear as a result of the summons."
The blocking maneuver implies that another dispute between Congress and the White House is likely to affect the judiciary is heading as the presidency is plagued by a forest of legal disputes.
That may be right for Trump, as it will postpone the political reckoning that could eventually happen and delay the publication of documents he wants to keep secret – such as his tax returns.
The White House seems to have far stronger arguments in the gloom and I. An untested area of leadership privileges than the president in his personal lawsuit for his financial records.
If Trump succeeds in thwarting McGahn's testimony, it may set a precedent that Congress would never be able to subject a member of a president's executive to cross-examination.
Democrats want to question McGahn about a plethora of evidence that Müller amassed to suggest possible presidential disabilities, including the revelation that he had ordered the then White House lawyer to dismiss the Special Adviser himself.
The President received potentially more disturbing news regarding the release by Congress of his former personal lawyer Michael Cohen on Monday of a non-public testimony to the Congress.
Sekulov's lawyers said Cohen was trying to blame others, arguing that it was against the legislature's logic. Take the word of a man currently in jail, partly because he lied to Congress.
Trump tries a trusted defense
Mazars, Trump 's auditing firm, will not have to stick to it. Judge Mehta claims that the Subpoena for another seven days to be completed.
To stop the surrender then, another court may need to intervene in the appeal proceedings Decision of politicizin g it – to call it somehow invalid because Mehta had been appointed by his predecessor Known is that he believes that justice can only be provided by a judge who shares his policy, a point of view contrary to democratic principles.
The President also resorted to partisan arguments that help him steer Washington's political wars and appeal to its base.
"The Democrats were very upset about the Müller report as it should be, but I think the country is very happy about it because there has never been anything like it."
But a lesson from the Monday's verdict is that Trump's personal political arguments and evasion maneuvers, though useful to survive a news cycle, are far less effective in court.