The Law Enforcement Assistance and Cooperation Treaty with Ukraine specifies that the designated officials of the two nations are the US Attorney General and the Ukraine Minister of Justice, (3.1.d.). The treaty binds those two offices--and so the usual rules in both nations, regarding those offices: In the Treaty. So from the New York Times, about the phone--Barbarous Anti-American sentiment is apparently what the White House has documented.
"A Justice Department official said that Mr. Barr had no knowledge of the call until the director of national intelligence and the intelligence community’s inspector general sent the department the whistle-blower’s criminal referral late last month, and that Mr. Trump has not spoken with the attorney general “about having Ukraine investigate anything relating to former Vice President Biden or his son.”
Political interference is not considered cause, stated in the Treaty provisions.
https://www.congress.gov/106/cdoc/tdoc16/CDOC-106tdoc16.pdf
Crow, James Crow: Shaken, Not Stirred!
(Red-Hatter waving takes on a new appearance. "Banzai! Surprise!" Attack on the USA apparently is supported--or on Ukraine, or Crimea!)