No, he's not. Marquis Leonard of Aramis' fief is the City of Leedor, not the world or Aramis. Also, it is his personal fief. It belongs to him because he is Leonard Bolden-Tukera, not because he is Marquis of Aramis. The Emperor could strip him of his title, but not his personal fief; it never was the Emperor's to hand out in the first place. Leonard is a local ruler who has been given a second job as an Imperial noble.
Hans
MAJOR terminology blunder there, Hans.
If it's a fief, it's granted by the emperor (or an archduke), and is Imperial property.
If it's personal property, it's axiomatically NOT a fief.
A fief is, by definition, lands granted by a liege to a vassal. Even in Traveller. See S11:LD N-Z
Fiefs: Patents of nobility, especially for service, may include fiefs of land. Fiefs are granted in a Letter of Enfeoffment separate from the patent of nobility. Fiefs are granted to the individual at the discretion of the Emperor and remain the Emperor's possessions. However, the fief conveys the right to use the land, to rent or lease it out and collect income from it. The fief is a convenient method for the Emperor to reward certain nobles.
(S11, p. 36. Color mine.)
Personal Fief is a near synonym of
demense, as opposed to of
see. (A demense is all those lands bound direct to the title, and which are not subinfeudated. A see is all the other lands associated with a given title. The Duke of Regina's See is all of the Regina Subsector; his fief is a chunk of land on Regina itself.)
Plus, it's not correct to the text, in any case.
"The Marquisate is a hereditary position which, on Aramis, has made him ruler of the planet." (TTA, p. 35)
"The Marquis, as head of the feudal technocracy of Aramis, grants a variety of subordinate positions in city government to citizens of Aramis and Leedor in return for money, pledges of loyalty, and other services." (ibid.)
Leedor on Aramis, as a Feudal Technocracy, is essentially an "imperial city"... it's a fief of a major noble. The rest of the world answers to him because he heads the largest city, and he heads the largest city because he's the Marquis whose fief is the city.