From what I've read on this, the problem arises from the fact that the hospital where these deliveries take place is now a
private hospital. It used to be a public hospital when Coburn was in the House. Once the hospital went private, the Senate Ethics Committee decided that his continued work there could be determined to be
an endorsement of that hospital.
By this standard, Senators should only be allowed to pump their books at public libraries and not book stores....but that ain't gonna happen.