improper was done - if the US wants an investigation, then they need to make the request. State/FBI isn't going to request a "fishing expedition" - this is a political action:
"Ukraine is ready to investigate the connections Joe Biden’s son Hunter had with the Ukrainian natural gas company Burisma Holdings, according to Anton Geraschenko, a senior adviser to the country’s interior minister who would oversee such an inquiry.
Geraschenko told The Daily Beast in an exclusive interview that “as soon as there is an official request" Ukraine will look into the case, but “currently there is no open investigation.”'
https://www.thedailybeast.com/ukraine-is-ready-to-investigate-bidens-sonbut-only-if-theres-an-official-us-request