Use the table's abbreviation

Warning²Federal courts, Illinois courts21st and 22nd editions

An institutional author's abbreviations come from tables T6 and T10, so a shortened word takes the table's own form, such as "Nat'l" or "Dep't", not a private contraction.¹

1. 1R. 15.1(e) Abbreviations; R. 15.1(d) Abbreviations. Tables: T6 Case Names and Institutional Authors in Citations; T10 Geographical Terms.
2. 2A warning: the form is usually wrong under the rule in note 1, and context can justify it.