Taxation is only sustainable if the general public complies with it. The theoretical public finance literature has interpreted tax constitutions as binding contracts by which the power to tax is irretrievably conferred by individuals to government, which can then levy any tax it chooses. However, in the absence of an outside party enforcing contracts between members of a group, no arrangement within groups can be considered a binding contract, and therefore the power to tax must be sanctioned by individuals on an ongoing basis. In this paper we show how the sustainability of taxation is linked with property rights and their enforcement. (This is a revision of 'Viable Tax Constitutions,' Warwick Economics Research Paper No. 683, 2003)