After studying at the universities of Vienna, Göttingen and Berlin, he became professor at the University of Lemberg in 1866, and in quick succession held similar positions at Prague, Strasbourg and Berlin.
[1] From 1872 Brunner devoted himself especially to studying the early laws and institutions of the Franks and other antique peoples of Western Europe.
He became a member of the Berlin Academy of Sciences in 1884, and in 1887, after the death of Georg Waitz, undertook the supervision of the Leges section of the Monumenta Germaniae Historica (MGH).
This was the first time that a legal scholar led a section of the MGH; Brunner oversaw an extensive overhaul of the section's program (the re-editing of the Capitularia and the Lex Alamannorum, then the Lex Burgundionum, and finally the Lex Baiuvariorum).
[2] Brunner wrote:[1] He is also the author of the German versions of The Sources of English Law.