Sains is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. Treaties between France and England placed …Sains is a commune in the Ille-et-Vilaine department in Brittany in northwestern France. Treaties between France and England placed Brittany under English rule. In 1402 the French and English were getting along a little better, after many decades of disputes in 1518 a treaty was signed giving England ownership of Brittany, hostages were handed over by the French as a guarantee that the treaty would be honoured.