Most formulations of human rights are drafted in such a way as to apply equally to citizens and do not increase, decrease or qualitatively alter the content of those rights on account of the citizen's membership of an ethnic group. Collective rights, by contrast, are not solely based on the citizen-state interface, but legally interpose the ethnic group between the state and the citizen. Thus citizens, either through choice or by compulsory designation, receive legal rights and duties not universally and equally, but according to the ethnic group of which they are members.
In the Roman Empire, for example, Jews possessed a special status and as such enjoyed specific rights as Jews, e.g. the right not to work on the Sabbath, or to recognise the divinity of the Emperor. Such rights were granted to the Jewish collective and thus to the individual Jew of the Empire by virtue of being Jewish so that the Jew was distinct from the Greek or Syrian or Celt in the Empire. The Ottoman Empire was governed so that each ethnic group in the Empire was defined on the basis of its religious community. Thus, people living in the same town but belonging to different faiths had different rights and obligations on account of their group membership. The British Empire too made effective use of collective rights: colonials were dealt with according to British justice, whereas in many cases tribal or customary law tried locals.
In Europe, though, under the influence of Enlightenment thought, which focused on human rights as applying universally to all human beings, the system of "collective" rights began to break down. In 1856 the Ottoman Empire introduced a constitution guaranteeing (in theory) equal rights and treatment for all its subjects regardless of national origin or religious affiliation. Likewise, in Europe, the movement for Jewish emancipation, based on the Jewish Enlightenment, predicated its calls for equal treatment for Jews on the grounds of a single universal standard of rights and that each person deserved equal treatment as an individual. (It is interesting to note (i) that the state of Israel is based a concept of collective rights for Jews, and (ii) that fundamentalist Muslim thought in the West today is moving towards an advocacy of collective rights for Muslims in secular societies.)
The implications of collective rights in contemporary society
Collective rights are rooted in an understanding of the human being as an individual, but also as a member of an ethnic community. The theory denies that all people should be treated equally as citizens and that people should be associated with the ethnic groups to which they belong with its specific system or rights and obligations.
Arend Lijphart coined the term "consociationalism" to describe the sharing of power between segments of society joined together by a common citizenship but divided by ethnicity. In a democracy collective rights would assume that each ethnic group has an elected body; e.g. Jewish Council, Muslim Parliament which would legislate for the ethnic group. Many questions are left floating around, however.
Is membership of an ethnic group determined by birth of by choice?
Can citizens be members of more than one ethnic group?
Can citizens change the ethnic group of which they are members?
What is the position of citizens who don't belong (or don't want to belong) to any of the groups?
Are there limits on the powers of ethnic groups? (e.g. can a group freely determine its laws)
What happens when the laws of one group impinge on those of another?
A personal opinion
I personally see the introduction of ethno-religious collective rights as a state of affairs where the national state is managing a group of Bantustans. The state could never be neutral between addressing what it saw as individual needs and the demands of the ethnic group councils. Establishing Christian ethnic councils would be have little support among the white majority in Britain and, in so far as such measures were adopted, the result would be less to provide collective rights to Christians than a means of excluding Muslims from institutions’ i.e. legitimising racism. For minorities, even if adults could ‘opt out’ of their Bantustan children and young people would be subject to state supported traditional authority which would deny them the rights and choices of the white majority.
In a liberal society there is nothing to stop two people in dispute going to a religious court to sort out their problem, and if both parties accept the solution that is fine. However the idea that the state, through recognition of collective rights, would enforce a non-universal religious based judgment on the parties is unacceptable to me.
For me if the political left strives to move away from humanist universalism and endorses state sponsorship of religion and segregation (either in principle or as part of a strategy of moving towards ‘revolution’) then in my view such people are no longer left-wing in any meaningful sense. Hatred of the injustices of capitalism is good politics, hating capitalism so that any enemy of capitalism becomes an ally is the politics of ideological bankruptcy.