The websites of political parties VVD (Liberal), SGP (Christian reform) and Denk (leftist) use tracking cookies to follow users' online activity without asking their permission. Personal information ends up at marketing companies via illegally placed cookies, and that is not allowed under the law. According to Aleid Wolfsen of the Data Protection Authority, it violates human rights. "People should be free to navigate the internet without being followed. This is embedded in the Constitution and European Treaties." Political preference is especially sensitive information, says Wolfsen.