Carlson is an associate professor of law and adjunct associate professor of political science at Wayne State University.

President Trump's refusal to hand over records to Congress and allow executive branch employees to provide information and testimony to Congress during the impeachment battle is the strongest test yet of legal principles that over the past 200 years have not yet been fully defined by the federal courts.

It's not the first test: Struggles over power among the political branches predate our Constitution. The framers chose not to, and probably could not, fully resolve them.