Add the comma that closes the clause

Error²Law reviews21st and 22nd editions

A footnote citation clause opens with a comma, so it closes with one too, unless the sentence itself ends there instead of carrying on.¹

1. 1R. 1.1(b)(ii) Citation clauses. Tables: B1.1 Citation Sentences and Clauses.
2. 2An error: the rule in note 1 allows one form, and this is not it.