De jure Duchies (and Kingdoms and Empires) in Crusader Kings 2 are an important aspect with direct impact on multiple core game mechanics. The de jure mechanic in Crusader Kings 2 has been implemented to add a fixed mechanic for both Titles and border disputation to the game. In addition to the Event-based territorial claims (via Fabricate Claims in the Chancellor missions), the de jure mechanic sets up a well integrated rule set tying together the concepts of Titles and Claims in a simple and powerful way.
What is De Jure?
The concept of de jure represents historical bonds shared between similar territories of the same feudal levels. For in-game purposes, it is probably more accurate to envision these ties as existing in the minds of the various Dukes and Kings than in the behavior or desires of the citizenry. Bordering counties can belong to the same de jure Duchy, Duchies (bordering, or maybe not with Dynamic Kingdoms) the same de jure Kingdom, and all kinds of stuff into de jure Empires.
De Jure Topics: