This paper explores the effects of linguistic diversity on equality before the law, by surveying sociolinguistic and applied research that investigates interaction between speakers of different languages in a variety of legal institutions, including genres such as courtroom talk, police interrogations, and asylum interviews. While the institutions have official languages that are used by agents working in them, many people who interact with them speak other languages and have limited or no proficiency in the official language. The paper examines how language choice is determined in such settings, considering factors such as legal statutes, language proficiency assessments, and language ideologies. It then investigates the indexical and pragmatic consequences of language choice for lay participants, whether they speak in the official language (their L2) or in another language (often their L1), but mediated by an interpreter. Demonstrating how interpreter-mediated interaction differs from interaction in the same language, the paper challenges the common assumption that competent interpreting can put a person in the same position as a speaker of the official language would be. Finally, alternative approaches to multilingualism in interaction and entextualization are explored, which address some of the disadvantages that speakers of non-official language face.