The European Court of Human Rights (ECtHR) has often been criticised for lacking clarity and consistency in its reasoning of balancing human rights against conflicting public interests. To reconcile national security interests with human rights protections, the ECtHR requires the interference with rights to be suitable for reaching the objective purported by the government. This article deals with how the ECtHR conducts the suitability test in national security cases, in line with two models under which a few representative test considerations can be categorised: Human Rights Priority Model and National Security Priority Model. To explain how each model works in a comparable sense, the article shall follow the same analytic structure and examine the manner of the ECtHR's test and the intensity of its scrutiny. The article finds that in compliance with the two models, the ECtHR applies the suitability test in a consistent and predictable way in national security case law.