California is challenging the historic status of American citizenship with measures to permit noncitizens to sit on juries and monitor polls for elections in which they cannot vote and to open the practice of law even to those here illegally. It is the leading edge of a national trend that includes granting drivers’ licenses and in-state tuition to illegal immigrants in some states and that suggests legal residency could evolve into an appealing option should immigration legislation fail to produce a path to citizenship.