A treaty from 2000 between the Ukraine and the United States requires the two countries to cooperate on law enforcement matters, a factor that may help to explain why President Donald Trump felt comfortable questioning the involvement of Joe Biden and his son, Hunter, in Ukrainian affairs, during a telephone conversation two months ago with Ukrainian President Volodymyr Zelensky.
The American and Ukrainian governments, it turns out, are legally required by treaty to render mutual legal assistance in criminal matters.