Use "C.F.R." for the code's name

Error²Federal courts, Illinois courts21st and 22nd editions

Each letter of an abbreviation takes its own period, and adjacent single capitals close up; the Code of Federal Regulations is abbreviated “C.F.R.”, not “CFR” or “C. F. R.”.¹

1. 1R. 14.2(a) Final rules and regulations; R. 6.1(a) Spacing; B14 Administrative and Executive Materials. Tables: R. 14.1 Basic Citation Forms.
2. 2An error: the rule in note 1 allows one form, and this is not it.