The reasoning is that the DOJ under Barr (and the administration in general) has no interest in cooperating with Congress or fulfilling their constitutional/legal obligations.
If the Congress really wants it can enforce its own subpoenas by putting anyone who refuses to testify in their own jail, without asking the DOJ for help. This is a power that hasn’t been used since 1934, and the current Congress has opted to work through the courts / make appeals to the electorate instead of applying it.
If the Congress really wants it can enforce its own subpoenas by putting anyone who refuses to testify in their own jail, without asking the DOJ for help. This is a power that hasn’t been used since 1934, and the current Congress has opted to work through the courts / make appeals to the electorate instead of applying it.