"To provide all possible information encompassed by your request...would constitute a vast and expensive undertaking," Bauer writes. "To the extent you are also seeking documents reflecting internal deliberations and communications, it also would implicate longstanding Executive Branch confidentiality interests."
You can read the entire letter here. Chairman Fred Upton (R-MI) launched his investigation in February, dinging Obama for falling short of his campaign pledge to conduct the deliberations publicly. This request might go to far, but there's likely bipartisan interest in knowing more about those negotiations, which many progressives blame for weakening the law.