The enactment of populist taxes targeted at aliens is a contemporary phenomenon in a number of countries. This paper discusses the additional taxation that many Australian jurisdictions have sought to impose on foreign ownership of property, against the backdrop of some of Australia’s international tax obligations. Such foreigner-specific taxes would appear to be incompatible with expansive non-discrimination clauses contained in a number of international tax agreements to which Australia is a party. Interestingly, nationals of polities with agreements that have no applicable non-discrimination clauses (such as the United States, the United Kingdom, Canada and China) or those of countries with no relevant tax treaty, might, pursuant to Australian constitutional law, also be able to rely on the aforesaid incompatibility for relevant relief. The ramifications of such incompatibility in terms of the potential for non-compliance with Australian domestic human rights legislation, and for potential private law actions for money had and received, will also be canvassed, along with likely ‘intergovernmental immunity’ considerations.