Sui generis
In local government, a "sui generis" entity is one that does not fit with the general scheme of local governance of a country. For example in England, the City of London and the Isles of Scilly are the two "sui generis" localities, as their forms of local government are both (for historical or geographical reasons) very different from those of elsewhere in the country. 
In a press conference during which reporters were trying to analyse his political personality, Huey Long said, "...say that I am "sui generus", and let it go at that."
Sui iuris
In civil law, the phrase sui juris indicates legal competence — the capacity to manage one's own affairs (Black's Law Dictionary, Oxford English Dictionary) — as opposed to alieni juris, which means someone under the control of another (such as a child or mentally incapable person might be). It also indicates an entity capable of suing and/or being sued in a legal proceeding in their own name (in personam) without the need of an ad litem. (A court appointed representative, acting on behalf of a defendant, that is deemed to be incapable of representing themselves).