In English, Maître Renard is just plain Mr. Fox
There is no English equivalent to the French Maître (Me) as a formal title or term of address for attorneys. When speaking or writing to a lawyer – be it an American attorney-at-law, or a British solicitor or barrister – one simply addresses them as Ms. or Mr.
In correspondence between lawyers in the US, it is customary but not obligatory to append Esquire or Esq. (preceded by a comma) to the colleague’s name in the address, as a sign of respect. In that case no title precedes the name. In other words,
Alex Fox, Esq.
Street
City
or
Prof. Alex Fox
Street
City
but not:
Dr. Alex Fox, Esq.
In the UK, Esquire is used more generally and does not necessarily suggest that the addressee is a barrister or a solicitor.
Esquire (or Esq.) is not used in the salutation in either the US or the UK however:
Dear Ms. Fox (and not Dear Ms. Fox, Esq.)
Similarly, British lawyers often have official titles that should be appended to their names in their address, but not in the salutation: Alex Fox, QC (Queen’s Counsel); Alex Fox, FBA (Fellow of the British Academy), but Dear Ms Fox and Dear Mr Fox.
When referring to a lawyer or lawyers for the opposing party in written or oral arguments before the court, it is common to speak of “counsel” for the plaintiff or the defense. Counsel may be singular or plural.
“Counsel for the defense has argued…” (for a single lawyer)
“Counsel for the plaintiff state in their argument…” (for a team of lawyers)