There is the concept that law only encodes the status quo, and directs course of action to maintain it. If something is not specifically forbidden but found deplorable, then the judgement will be subsumed under the basic blanket statements of the constitution--often without such big words but rather common sense.
In this case, it is specifically forbidden to go and take other peoples money for inventing an algorithm that you had invented before. That's common sense as encoded in the legal code, for each and every method that could optain the money, and these also count for the patent office, who have been however excempt in limited cases.
The law rarely speaks of forbidding; cp pro-hibition, OE forehaeldan, pro of the same root as forbid or equivalently Ger verbieten (with ver- in many cases nevertheless not always carrying a negative connotation, ca "off, away", or rather "before", cp ante, anti for analogy).
It rather speaks of rights, and modern philosophy assumes that everybody has basic human rights before the law, not to say independent of the law.
Corolarily: Of course it's not forbidden to accept reimbursement, donations, etc, but it can't be forced, not through the patent office.
Cp further "statutory interpretation" (with a degree of three links distance to de.wiki/exegesis, and one to Auslegung, viz teleologic exegesis), surely understood as statute.
I compare various words around standing, good standing, Ger anständig "good standing", verständig, understanding (Ger unterstellen seems to come through a sense "standing under shelter, be protected by believe, believe, allege, discredit, defame; cp support, Ger unterstützen); staendige Rechtssprechung "precedented sentencing" (ca steady, upright or continuous), and especially, which would answer your question: legalese statthaft "admissable, according to formal requirements; ? respectable" (as correlated to legalese zulässig "permissable, allowable; tolerable", begründet "justified, acceptable; ? well grounded"; cp statt finden "to take place"), Middle High German statehaft "able, equipped, esteemed, fortunate", Old High German unstatahaft (8th century; cp e.g. undead); Pfeiffer/DWDS also compared gestatten "allow", status quo. Also cp Gestalt "forma", Gestell "matrix, frame, support, rig".
That said, statutory is lexicalized chiefly as if from constitution. Through Latin we find related destitute ("lacking in something, forsaken", i.e. still having the death penalty), institute, etc, but I see no term other than unconstitutional that would fit your request in the modern context. Given the above allusion to pro (opposite of contra if I say so myself), as well as to "*public opinion" (i.e common sense) I'm inclined to suggest prostitute "to set up in public", but that's obviously nonsense; another contrast to con is sin "without" (Spanish as in "caffe sin lecho") and sinfull fits the underlying sense of law in many ways, however unknown the etymology.
irregular also comes to mind. But the exact terminus technicus for what you are looking at I don't know.
A correlate to de legis (by law) is de facto (for a fact). Like, many languages or only de facto official lamguage of a country. It is after all impossible to create an official law in an official language to designate the official language unless it already were the official language.
That said, there's probably a legal latin phrase meaning exactly what your example suggests. In textual canon there is:
Expressio unius est exclusio alterius ("the express mention of one thing excludes all others"), or "Expression of one"
