illegitimate
adj.adj. something that is not allowed by the rules or the law. It can also describe a child born to parents who are not married, though this is an old-fashioned way to use the word.
adj. contrary to established laws, rules, or logic; unauthorized. Historically used to describe offspring born out of wedlock, though this sense is now largely archaic or restricted to legal contexts.
The judge ruled that the evidence was illegitimate.
The opposition party claimed the election results were illegitimate due to widespread voting irregularities.
While the regime maintained a veneer of democracy, international observers argued that its power was illegitimate because it lacked the genuine consent of the governed.
First attested in 1536, from Latin illēgitimus, most likely an adapted borrowing of Middle French illegitime, equivalent to il- + legitimate, see -ate (etymology 1, 2 and 3).
Often used to describe abstract concepts like power, authority, or arguments rather than physical objects.