You really asked that? O.k. FYI
https://www.justice.gov/jmd/organization-mission-and-functions-manual-attorney-general
Note No.1: Represent the United States in Legal Matters.
It’s a policy matter, not a legal matter. The USG is the client and decides what position it wishes to hold. The lawyer can provide legal advice, but the client decides what position it wants its lawyer to take. If this story is correct, which I doubt, Barr should not be involved in election strategy.