Pr is a natural right if there are more than two people

Since we are not alone in the world and other people exist then it is natural to have a government and further it is natural to have a democracy. No state can be valid if it does not have a mandate from the people which is derived from democracy. All states must be democratic and if there are more than two people in the world then it is a requirement to have a state... otherwise property rights will be determined by force alone.

If there are only two people then it can be assumed that each will vote for themselves and there is no need for (government and) democracy. It is when there are more than two people that a state can be valid and the majority can protect themselves from the aggression of the minority.

If there are more than two people it is natural and preferable to have a democratic government so that property rights are determined by consensus and not theft. It is a natural right to form a government if it is democratic and by extension full democracy is a natural right. (We have no right to form a state without democracy.) We do not have full democracy if we must vote tactically as with first-past-the-post and so pr is a natural right. Proportional representation is a natural right because whilst we have a right to form a democratic government we do not have a right to oppress democracy. Since we do not have a right to oppress democracy (and yet we have a right to form a government) then pr is a natural right.

None of the above is inconsistent with the non-aggression principle.