The teacher certification system was introduced in Sweden on July 1, 2011,through the Act (2011: 189), reforming the Swedish Education Act. The purposeof the new certification system was to increase the quality of Swedish schools, toraise the status of the teacher profession and to clarify what preschool andschoolteachers can teach. As a result of this new system, only certified preschooland schoolteachers can be permanently employed in Swedish schools, and onlycertified schoolteachers are able to set grades on their own.The certification of preschool and schoolteachers can be revoked if at leastone of the conditions stated in Chapter 2, Section 23, Paragraph 2 in the SwedishEducation Act (2010:800) is met. The Teachers Responsibility Board (Lärarnas-ansvarsnämnd) was formed, in part, in order to make decisions regarding revo-cations of teacher certifications. The Teachers Responsibility Board´s decisionscan be appealed to the Administrative Court.The purpose of this essay is to investigate whether Chapter 2, Section 23, Par-agraph 2, in the Swedish Education Act about revocation of preschool andschoolteacher’s certification fulfills the requisites of clarity and predictability,which follow from the constitutional principle of legality.Case laws from the Teachers Responsibility Board and from the Administra-tive Court have been used, to a large extent, in this essay to examine how thedecision-making bodies have interpreted and applied the aforementioned legalprovision.The conclusion is that Chapter 2, Section 23, Paragraph 2, in the SwedishEducation Act doesn´t fulfill the requisites of clarity and predictability that followfrom the constitutional principle of legality because this legal provision is vagueand ambiguous.The teacher certification system is a relatively new system, and there is a lackof research on the subject, which justifies the need to investigate this topic fur-ther.