Section 1. Part II of the Manual for Courts-Martial, United States, is amended as follows: . . . (r) R.C.M. 503(a)(1) is amended to read as follows: (iv) where a convening authority determines it to be impracticable to meet the requirements of R.C.M. 503(a)(1)(B)(i)-(iii) due to exceptional circumstances, a sufficient number of detailed members to allow for the randomization process in R.C.M. 911. Exceptional circumstances include circumstances in which the minimum required numbers of detailed members are not available due to a military necessity or exigency;