Wherever persons agree concerning any particular subject, that, in a court of equity, as against the party himself and any claiming under him voluntarily or with notice, raises a trust.

Explanation

(English-origin maxim.) When parties agree on a matter, equity will enforce that agreement as a trust against the promisor and anyone claiming under him with notice — this is the foundation of constructive trusts arising from consensual dealings.

Where this applies

• Two business partners agree that one will hold a building in trust for the other, and when the holder tries to sell it, equity enforces the agreement as a constructive trust.
• A father verbally promises his son that a piece of land will be held for the son's benefit, and when the father dies, equity imposes a trust on anyone who inherited the land with knowledge of the promise.
• An employer and employee agree that patent rights developed on the job belong jointly to both, and when a successor company tries to claim sole ownership, equity enforces the original agreement as a trust.