While the right to live in a democracy can be tantamount to the right to life... international law does not recognise the right of an individual to live in a democracy.
The Universal Declaration of Human Rights does include at Article 21(1), as he himself notes, that 'Everyone has the right to take part in the government of his country, directly or through freely chosen representatives', but Rubinstein regards this as an empty formula compatible with voting in a Soviet-style one-party state. I'm not so sure about that: 'freely chosen representatives' can be interpreted in more than one way, but 'freely' either means freely or the relevant right is not being realized. In any case, Rubinstein argues that it is pragmatic political calculations that have led to the absence of an effective right to live in a democracy from international human rights instruments. He speaks of...
... the need to accommodate and placate victorious Soviet Communism after World War Two... [and later] the composition of the UN itself – the majority of whose members are non-democratic in some way – as well as... the fear of causing a split within the international community.
I would see something else, or at any rate something more, as having been at work, a doctrinal premise: namely, the principle of national self-determination. If there is a universal right to national self-determination, then there cannot be a universal right to live in a democracy so long as self-determination is thought to allow nations to choose their own form of government. Here one might argue that if this is to be a genuine choice then there must be democratic means of registering it; but I think the counter-argument would be that peoples can choose in other, more negative, or implicit, ways. If they tolerate, or merely live with, forms of rule which are less than democratic, then this may be viewed, practically-speaking, as a kind of choice. Put another way, democracy has to be 'taken on' by any national populace, by their campaigning for it, fighting for it, or at least receiving it willingly in circumstances - such as defeat in war - where democracy has been delivered by the armies of an external power.
I don't say that the above position is without its problems. It isn't. But I assume it to be standard as a way of reconciling national self-determination with the absence of an individual's right to live in a democracy. National self-determination presupposes ways of construing the collective national will that do not depend on genuinely democratic elections or expressions of that will through mechanisms such as the referendum.
All that said, Rubinstein has a point. The right to live in a democracy is important as a powerful protection against arbitrary and lethal state power, and belongs with other fundamental human rights. Including it in international treaties and human rights documents would give support to democrats everywhere, especially those living under dictatorship. Today, the notion that this or that people really doesn't want democratic government can be tested (where it is not just a blatant rationalization for monopolistic power) by the usual mechanisms of democratic choice. Should it prove to be the case somewhere that people vote for their own exclusion from democratic rule, then they will really have chosen not to avail themselves of the right to live in a democracy, but it will then be clear that that was their (majority) choice. There would need to be free, and possibly even assisted, emigration.