within the pale

The phrase within the pale, meaning to stay within the limits of law or decency, was in use by the mid-17th century. The phrase is a reference to the general sense of boundary, not to any of the particular places, such as the English pale in Ireland, which bore that name, or the Pale of Settlement, in Imperial Russia. Out of the many districts established by England (Cork, Dublin, Drogheda, Waterford, and Wexford), only a select few followed the laws established by England, hence "within the pale" and beyond the pale.

来源：wiktionary