Does the Social Contract Have a Dotted Line?

Today is the 706th anniversary of the death of William Wallace, a Scottish knight who led the revolt against Edward I who claimed rule over Scotland. When tried for treason, his defense was that he could not be guilty of treason against a government to which he never swore allegiance. The defense failed in practice, but raises an interesting question -- if the basis for civil society is, as Locke, Hobbes, Rousseau and others have argued, a social contract, then can you be made a party to this contract against your will? In general, for a contract to be valid, one has to enter into it freely, but is this also so with the social contract that distributes rights and responsibilities within the community into which you are born? Is mere presence the equivalence of informed consent? Does the social contract have a dotted line?