I’ve heard it traced to early US retained firms in the 1950s, but I’ve never seen a primary source. My standard is a 12‑month off‑limits to direct competitors because it protects leadership pipelines and keeps assessment work clean — does anyone have the first documented reference?
One place I’ve found early, dated “off‑limits” language is in exhibits to court‑filed engagement letters — bankruptcy dockets often attach the retainer with the clause — so run a PACER search for “executive search” in 1960s–70s cases: https://pacer.uscourts.gov. I also default to a 12‑month off‑limits for direct competitors, but I carve out references and alumni lists because they don’t impact leadership pipelines the same way. Happy to trade sources if you turn up anything pre‑’59.
I’ve had the best luck finding early mentions in NYT/WSJ classifieds — search 1955–65 for Spencer Stuart or Heidrick & Struggles with the phrase “we will not recruit from clients”. @sanders_j56 is right on court files, but ads give you a clean, date-stamped source that matches your 1950s hunch. If someone can pull a ’56–’58 hit, that’s probably your earliest contemporaneous cite.
But building on @a_jones71, run ProQuest or Newspapers.com with the exact phrase “we will not recruit from clients” and filter to ads 1953–62; those classifieds often carry the earliest boilerplate before any code was published. It’s like hunting the first “no poaching” sign — if you turn up a pre‑’59 clipping, can you share the date line?
Quick example: I tracked the earliest formal client non‑solicit in the AESC Code — a 1961 pamphlet at NYPL — so I’d ping AESC directly (https://www.aesc.org) and ask for their first Code/Bylaws scan; they’ll usually email it same day, @a_jones71. If you land anything earlier, mind sharing the dateline?