21 U.S. Code § 396 - Practice of medicine
Nothing in this chapter shall be construed to limit or interfere with the authority of a health care practitioner to prescribe or administer any legally marketed device to a patient for any condition or disease within a legitimate health care practitioner-patient relationship. This section shall not limit any existing authority of the Secretary to establish and enforce restrictions on the sale or distribution, or in the labeling, of a device that are part of a determination of substantial equivalence, established as a condition of approval, or promulgated through regulations. Further, this section shall not change any existing prohibition on the promotion of unapproved uses of legally marketed devices.
Source(June 25, 1938, ch. 675, § 1006, formerly § 906, as added Pub. L. 105–115, title II, § 214,Nov. 21, 1997, 111 Stat. 2348; renumbered § 1006,Pub. L. 111–31, div. A, title I, § 101(b)(2),June 22, 2009, 123 Stat. 1784.)