Sec. 248. [8 U.S.C. 1258] 2/ (a) The Secretary of Homeland Security may, under such conditions as he may prescribe, authorize a change from any nonimmigrant classification to any other nonimmigrant classification in the case of any alien lawfully admitted to the United States as a nonimmigrant who is continuing to maintain that status and who is not inadmissible under section 212(a)(9)(B)(i) (or whose inadmissibility under such section is waived under section 212(a)(9)(B)(v)) , 1/ except 2/ (subject to subsection (b)) in the case of-

(1) an alien classified as a nonimmigrant under subparagraph (C), (D), (K), or (S) of section 101(a)(15) ,

(2) an alien classified as a nonimmigrant under subparagraph (J) of section 101(a)(15) who came to the United States or acquired such classification in order to receive graduate medical education or training,

(3) an alien (other than an alien described in paragraph (2)) classified as a nonimmigrant under subparagraph (J) of section 101(a)(15)who is subject to the two-year foreign residence requirement of section 212(e) and has not received a waiver thereof, unless such alien applies to have the alien's classification changed from classification under subparagraph (J) of section 101(a)(15) to a classification under subparagraph (A) or (G) of such section, and

(4) an alien admitted as a nonimmigrant visitor without a visa under section 212(l) or section 217 .

(b) 2/ The exceptions specified in paragraphs (1) through (4) of subsection (a) shall not apply to a change of nonimmigrant classification to that of a nonimmigrant under subparagraph (T) or (U) of section 101(a)(15) .