15 U.S. Code § 6305 - Registration
Each boxer shall register with—
(b) Identification card
A boxing commission shall issue to each professional boxer who registers in accordance with subsection (a) of this section, an identification card that contains each of the following:
(B) The social security number of the boxer (or, in the case of a foreign boxer, any similar citizen identification number or professional boxer number from the country of residence of the boxer).
Each professional boxer shall renew his or her identification card at least once every 4 years.
(c) Health and safety disclosures
It is the sense of the Congress that a boxing commission should, upon issuing an identification card to a boxer under subsection (b)(1) of this section, make a health and safety disclosure to that boxer as that commission considers appropriate. The health and safety disclosure should include the health and safety risks associated with boxing, and, in particular, the risk and frequency of brain injury and the advisability that a boxer periodically undergo medical procedures designed to detect brain injury.