Fundamental legal principles and rights may function as a check on legislative power protecting citizens against arbitrary interferences of tax legislation with their lives. We’ll start with a description of the fundamental protection of individual rights that exists under Dutch national law and the agencies that have primary responsibility for protecting those rights. This principle of equality is an important judicial instrument to check seriously flawed tax legislation. The testing of tax law against this principle of equality can act as a case study to gain more insight into the topic of constitutional review. Acts of Parliament are tested against international treaties (Article 14 European Convention of Human Rights (ECHR), in conjunction with Article 1 of Protocol No. 1 ECHR (Article 1 P-1 ECHR), and Article 26 International Covenant on Civil and Political Rights (ICCPR). In terms of the method of judicial interpretation, we will show that the Dutch Supreme Court always demands an objective and reasonable justification for any inequality of treatment. This is in conformity with the method applied by the European Court of Human Rights (ECtHR). As for testing tax law against the principle of equality, the Supreme Court acknowledges the wide margin of appreciation of the legislator. If the Court establishes a violation of the principle of equality, it acts very cautious. We acknowledge that the Dutch Supreme Court has initially made a valuable contribution to the constitutional system of checks and balances – underlining the significance of the principle of equality for fair tax legislation. However, in our opinion, the Supreme Court should pay less deference to the policy views of the tax legislator. Next, we’ll discuss the testing of tax legislation against Article 1 P-1 ECHR (right to property). Both the Supreme Court and ECtHR observe a (very) wide margin of appreciation vis-à-vis the legislature if the so-called of the public interest test and the proportionality test are applied. This margin is only ...