▁but ▁refused ▁to ▁leave ▁Brit t any ▁even ▁when ▁offered ▁cov et ed ▁court ▁positions ▁in ▁Paris . ▁ ▁In ▁his ▁jud icial ▁capacity , ▁he ▁frequently ▁cl ashed ▁with ▁other ▁juris dict ions ▁such ▁as ▁that ▁of ▁the ▁Par lement , ▁which ▁he ▁considered ▁ignor ant ▁of ▁Bre ton ▁custom s . ▁His ▁principal ▁legal ▁work ▁is ▁the ▁influ ential ▁Nouvelle ▁cout ume ▁de ▁Bret agne ▁( 1 5 8 0 ), ▁a ▁compilation ▁of ▁custom ary ▁Bre ton ▁law . ▁In ▁that ▁work , ▁D ' Ar gent ré ▁fought ▁against ▁the ▁influence ▁of ▁French ▁and ▁Roman ▁law , ▁which ▁he ▁considered ▁over ly ▁proced ural ▁and ▁in quis itive , ▁un mer c iful ▁to ▁the ▁weak , ▁and ▁det r iment al ▁to ▁individual ▁liberty . ▁ ▁His ▁work ▁as ▁a ▁historian ▁also ▁emphas ised ▁the ▁historical ▁independence ▁of ▁Brit t any . ▁The ▁Est ates ▁of ▁Brit t any ▁commission ed ▁him ▁in ▁ 1 5 8 0 ▁to ▁write ▁a ▁Histoire ▁de ▁Bret agne , ▁which ▁was ▁prompt ly ▁seized ▁on ▁the ▁order ▁of ▁Henry ▁III ▁for ▁" ind ign ities ▁against ▁King ▁and ▁real m ". ▁The ▁book ▁was ▁only ▁allowed ▁to ▁appear ▁in ▁ 1 5 8 8 , ▁with ▁extensive ▁c ensor ship ▁of ▁sensitive ▁pass ages ▁rel ating ▁to ▁the ▁history ▁of ▁French - Bre ton ▁relations . ▁However , ▁c land est ine ▁repr ints ▁of ▁the ▁un ed ited ▁work ▁remained ▁widely ▁available . ▁ ▁He ▁was ▁also ▁well ▁known ▁for