This thinking finds its way into federal laws that prohibit kickbacks for medical referrals and forbid doctors to own part interests in providers they refer business to.
Rules range from the 1996 Health Insurance Portability and Accountability Act (HIPAA) which can be a major source of confusion on privacy and security issues, to the 1989 Stark Law which regulates doctor referrals, to the Corporate Practice of Medicine laws which prohibit businesses from employing physicians, and forbid doctors from splitting fees with non-doctors.
However, U.S. election laws prohibit campaign contributions from overseas sources, and also forbid funneling money through front groups that hide the true source.