This essay scrutinizes Swedish legislation 1220-1360 from an institutional economic point of view inspired inter alia by Douglass C. North. Several books of law for different counties (sw. landskapslagar), as well as other kind of legislation, were worked out during the period and it was claimed that they were drafted to meet a changing society. My conclusion is that the real purpose was the opposite, i.e. that the upper strata tried to change society through legislation. In general were economic institutions hostile to a free exchange in favour of several compulsory institutions as slavery and serfdom, with the remarkable exception of the Town Law (sw. Stadslagen) in the 1350's that points in a modernizing direction. I've also come to the conclusion that the famous Swedish mining sector (sw. bergsbruket) came into being in spite of the ruling aristocratic classes. Much more was it a creation of gentile men and women witch in the fifteenth century contributed to the formation of two new estates in the Swedish parliament, burghers and peasants.