His law I translated into a foreign language (7)
I believe the answer is:
swahili
'a foreign language' is the definition.
'his law i translated' is the wordplay.
'translated' indicates anagramming the letters.
'his'+'law'+'i'='hislawi'
'hislawi' is an anagram of 'SWAHILI'.
'into' is the link.
(Other definitions for swahili that I've seen before include "Lingua franca of East Africa" , "Language widespread in East Africa" , "African people" , "Language of Kenya and lingua franca of other African areas" , "Major Bantu language widely used in E Africa" .)