The EU is demanding that, in return for a new deal, the UK must come up with a solution to the Irish backstop problem. But since the UK will happily leave with no deal, the EU will have to find a solution anyway. Let the Romans help out.
Latin foedus (cf. ‘federal’) meant a treaty that guaranteed peace and friendship between Rome and another state, in perpetuity. There were two standard models. A foedus aequum (‘equal’) put both parties on an equal footing. The first we hear of between Rome and the local cities of Latium agreed eternal peace, mutual assistance against enemies, equal sharing of spoils and speedy settlements of commercial disputes. Here both parties wanted exactly the same outcome.
A foedus iniquum (‘unequal’), struck when an enemy had been defeated, compelled the second party to acknowledge Rome’s sovereignty and to provide military forces on demand. Here a winner imposed conditions on a loser. This is how the EU is currently acting: you come up with a backstop solution we like, or else.
But there is another way, demonstrated by a peace-time treaty struck between Rome and Carthage in 507 bc, designed to reconcile conflicting interests (well before the devastating Punic Wars between the two states). It was needed because, two years earlier, Rome had become an independent republic by driving out its Etruscan king. This set alarm bells ringing in Carthage, a powerful North African trading nation which already controlled Sicily, because it had extensive commercial links with the Etruscans to the north and south of Rome. So the new balance of power had to be addressed. For Rome it was vital to assert that Rome, not the Etruscans, now controlled Latium; the treaty warned Carthage off interfering in any Latin city. Carthage likewise needed to protect its commercial interests against any Roman ambition to interfere; so the treaty controlled Rome’s access to the African coast and Sicily. Here, then, two sides met to create a treaty out of different needs.
The EU and the UK also have conflicting reasons for wanting the backstop problem solved. So chuck the schoolboy games-playing and team up like Rome and Carthage to solve it.