Sentence:  But feudalism also contained another principle, and that was, that within his own territory each lord was absolute; his suzerain could not interfere with his jurisdiction; infangthief and <WSD>outfangthief</WSD> implied a very perfect and intelligible power of hanging and imprisoning as he pleased. 
Meaning of the word marked with <WSD> tags:  A privilege of some feudal lords permitting them to execute summary judgment upon all thieves captured "within" their estates, regardless of their origin.