In 1993, the European Court of Human Rights was called upon to rule on a landmark case concerning religious freedom: Kokkinakis v. Greece. This case serves as a clear example of the profound impact that religious illiteracy can have in shaping public policies, legal rulings and individual's freedoms. Mr. Kokkinakis was indeed convicted for attempting to convert others to his religion, as national authorities had failed to recognize and understand, among other issues, that proselytism represents a core practice in Jehovah's Witnesses faith. This paper aims to explore, analyse and reconstruct the history of European key cases, focusing on how the lack of "functional understanding" regarding the beliefs, doctrines and practices of religious communities has manifested in judicial national and international rulings.