26 USC 1287 - Denial of capital gain treatment for gains on certain obligations not in registered form

(a) In general 
If any registration-required obligation is not in registered form, any gain on the sale or other disposition of such obligation shall be treated as ordinary income (unless the issuance of such obligation was subject to tax under section 4701).
(b) Definitions 
For purposes of subsection (a)
(1) Registration-required obligation 
The term registration-required obligation has the meaning given to such term by section 163 (f)(2) except that clause (iv) of subparagraph (A), and subparagraph (B), of such section shall not apply.
(2) Registered form 
The term registered form has the same meaning as when used in section 163 (f).