https://www.law.cornell.edu/wex/unjust_enrichment
https://en.wikipedia.org/wiki/Unjust_enrichment
https://www.investopedia.com/terms/q/quasi-contract.asp
IMPOSSIBLE CONTRACT - One which the law will not hold binding upon the parties, because of the natural or legal impossibility of the performance by one party of that which is the consideration for the promise of the other.
IMPOSSIBILITY - That which, in the constitution and course of nature or the law, no man can do or perform.
An act is physically impossible when it is contrary to the course of nature. Such an impossibility may be either absolute, i.e., impossible in any case, (e.g., to stop earth rotation) or relative (sometimes called "impossibility in fact"), i.e., arising from the circum stances of the case (e.g., for A. to make a payment to B.,he being a deceased person). To the latter class belongs what is sometimes called "practical impossi bility," which exists when the act can be done, but only at an excessive or unreasonable cost. An act is legally or juridically impossible when a rule of law makes it impossible to do it; e.g., for A. to make a valid will before his majority. This class of acts must not be confounded with those which are possible, although forbidden by law, as to commit a theft. An act is logically impossible when it is contrary to the nature of the transaction, as where A. gives property to B. expressly for his own benefit, on condition that he transfers it to C.
It is now recognized that a thing- is impossible in legal contemplation when it is not practicable; and a thing is impracticable when it can only be done at an excessive and unreasonable cost. Transatlantic Fin. Corp. v. United States, 363 F.2d 312, 315.
IMPOSSIBILIUM NULLA OBLIGATIO EST - There is no obligation to do impossible things.