The notes say the same mechanism shows up in workplaces and institutions, and then leave it for a different essay. The named specimen is already in the transition literature.
Spain's pacto del olvido was an informal agreement among the main parties after Franco's death in 1975: do not prosecute the dictatorship, do not put the Civil War back on the daily agenda, treat "national reconciliation" as the reason to stay quiet. It is not a clause in the 1978 Constitution (referendum 6 December 1978). The legal proxy is Ley 46/1977, of 15 October — the Amnesty Law — which covered political acts and also authorities, officials, and police who had violated "the rights of persons." Zapatero's Ley 52/2007 (Historical Memory) was treated by its opponents as a breach of that understanding, not as ordinary legislation. Baltasar Garzón's 2008 inquiry into Franco-era disappearances ran into the same wall: the Supreme Court kept the amnesty in force.
O'Donnell and Schmitter, in Transitions from Authoritarian Rule (1986, ch. 4), define a pact as "an explicit, but not always publicly explicated or justified, agreement among a select set of actors" that resets the rules of power on mutual guarantees of "vital interests." They flag Spain as a case of repeated pacts. That is an implicit treaty among power-holders: visible when someone tries to exhume it, invisible in the constitution a tourist can buy.
Competing account: a lot of elite "treaties" are not implicit in the essay's sense. They are written, and the writing is the point.
Joe Slovo's "Negotiations: What room for compromise?" (The African Communist, 3rd quarter 1992) floated a sunset clause: compulsory power-sharing for a fixed number of years, no permanent minority veto. The ANC's National Executive took it. Act 200 of 1993 then put it in public text. Section 80: the first President sits five years from the National Assembly's first sitting. Section 88: a party with at least 20 seats gets Cabinet seats in proportion. Section 236: existing public servants continue in post; pensionable salary is not cut. The 1996 Constitution did not re-entrench a government of national unity. The sun set on a date you can cite.
Chile went the other way and also wrote it down. The 1980 Constitution (plebiscite 11 September 1980) locked "protected democracy": designated senators, a National Security Council with a military majority, commanders the president could not remove. The binomial electoral rule — two seats per district, the leading list needs about double the runner-up to take both — lived in organic law (Ley 18.700 of 1988, Ley 18.799 of 1989), not in the constitutional articles a foreigner reads first. The 1989 reform package (plebiscite 30 July) kept those locks and raised the amendment bar on key chapters to two-thirds.
The smallest claim this changes is "power-holders run the same unspoken constitution as a couple." Alternative: some elite bargains are O'Donnell pacts — explicit among the parties, not always public — and some are constitutions. They differ on whether a clerk can name the clause. Spain's forgetting is not in the 1978 text. South Africa's GNU is s. 88. Chile's binomial is an organic law with a supermajority. If the next essay cannot say which of those three objects it is talking about, "implicit treaty" at state scale is a suitcase.
He already leaves institutions for a different essay, and he stays at two people on purpose. Couples, Mask, Shared Skeleton — that object is not being asked to do Spain.
What still is not covered is the cut you just named. An implicit treaty, on his usage, is unconscious to its bearer and surfaces as a moral insult. O'Donnell's pact is explicit among the people who signed it and hidden from everyone else. Those are not the same invisibility. The deferred essay has to pick, or the word "implicit" will mean "unwritten," "unconscious," and "denied in public" at once.