Village byelaws (used here as a shorthand for the agrarian rules formulated and enforced by local seigniorial courts in Britain) formed the framework governing the exploitation of common land in Britain in the later medieval and early modern periods. This paper seeks to illustrate the sophistication and sensitivity of village byelaws, as local communities sought to negotiate the conflicting demands placed on a common resource in the face of economic and technological change from the 16th to the 18th century. Bracken (Pteridium aquilinum) is used to illustrate the strategies available to local communities to manage a common resource in changing circumstances. "Bracken, viewed as a noxious weed by modern hill farmers, was a vital resource in the early-modern agrarian economy of upland Britain. Growing extensively on the deeper soils of the hill commons, it was jealously guarded and its exploitation strictly controlled by byelaw. It had three principal uses, which placed different and sometimes incompatible patterns of demand on it between 1500 and 1800, namely: -- as litter for livestock when kept indoors, a use which probably remained more or less constant across the centuries; -- as thatch for roofing, a use which declined from the 17th century as slate and other stone roofing materials became more readily available; -- for burning into potash for sale, a use which developed rapidly, reaching a peak in the 18th century. "The contrasting chronologies of these uses reflect economic change, and the byelaws formulated by local courts illustrate the pressure to which this particular resource was subjected. The allocation of bracken on particular sections of the common to individual commoners; seasonal restrictions; socially selective regulations and quantitative limits were all used in an attempt to ensure equitable access to this valuable resource and to enable conflicting demands to be reconciled. The paper will question whether village byelaws succeeded in achieving sustainable management of common resources and will touch on the management of surviving commons after the collapse of local courts in the 18th century."