The following is a news analysis.
There has been an understandable (and predictable) effort by President Trump's opponents within the State Department and beyond to controversialize his foreign policy practices.
Among the supposed controversies is Trump's use of his personal adviser and attorney Rudy Giuliani, Energy Secretary Rick Perry, Special Envoy Kurt Volker, U.S. Ambassador to the European Union Gordon Sondland, and Director of Office of Management and Budget Mick Mulvaney to implement Ukrainian diplomacy.
Trump critics and some in the media have incorrectly termed that as "shadow diplomacy."
Impeachment witness Ambassador William Taylor took great pains to repeatedly called this an "irregular channel," implying there was something sinister and wrong-- maybe even impeachable-- about the arrangement.
In fact, the resisting diplomats are the ones who are conducting shadow diplomacy when they are acting contrary to the president's wishes. Under the U.S. Constitution, the president directs all foreign policy; not the other way around.
Along those lines, there was something of a silent bombshell that nobody flagged in last week's impeachment testimony from Ambassador Taylor.
Taylor testified that he understood it was President Trump's desire to lock in a commitment from Ukraine to launch a corruption investigation by having the president, Vlodymyr Zelensky, say so on CNN. But Taylor further testified that he did not want the CNN interview to happen, and "sought assurances from Zelensky that he would not do so."
Under what authority did Taylor resist the President's foreign policy-- presumably behind his back?
Taylor and others also testified they assumed President Trump was seeking a campaign 2020 quid pro quo from Ukraine, and that they resisted that, too. We now know that Trump never mentioned the 2020 campaign-- at least there's no testimony or documentation so far that he did. He discussed investigating corruption tied to the 2016 election.
And we also know that quids pro quo -- although one was not consummated in the Ukraine case -- are a common and necessary part of foreign aid.
So, under what authority did these diplomats, who are tasked with implementing the president's foreign policy, assume his motivations as nefarious (having never met or spoken with him) and resist his policy desires?
Much of what they criticized isn't controversial at all-- except to the extent it's President Trump who's making the decisions. And, at times, his decisions are contrary to the opinions of some long-established diplomats.
What follows below is a description of the U.S. president's authority when it comes to who he can appoint to conduct diplomacy.
It was written in 1960 by Henry Wriston, President Emeritus of Brown University; Chairman of the Secretary of State's Public Committee on Personnel, 1954-56; President of the American Assembly, Columbia University; author of "Strategy of Peace," "Diplomacy in a Democracy" and other works.
Wriston's description makes clear that President Trump's use of Giuliani, Volker, Sondland and anybody else he pleases is clearly within his authority-- not "irregular" or sinister "shadow diplomacy."
Quids pro quo and using personal representatives to conduct diplomacy are not controversial.
The practice of diplomats going rogue to pursue their own foreign policy contrary to the president's wishes is controversial.
Regarding the impeachment debate at hand, the main valid question, which has not been well-defined, is whether President Trump improperly attempted to direct foreign policy solely for his personal, political benefit and/or to the detriment of U.S. interests. He says no. His enemies say yes.