The aim of this study was to investigate how social workers on a Chief Guardian unit work from their conditions when recruiting guardians. More specifically, we wanted to see how the law, the practise and the professionals’ tacit knowledge affect their judgement of guardians and how the organisation and the government of the Chief Guardian unit affect their work. The Chief Guardian unit is a municipal supervisor that control and supervise the work of the guardian. Media has criticized the Chief Guardian unit, by highlighting examples of unfit guardians. The Swedish National Audit Office (Riksrevisionen) has expressed a number of shortcomings of the supervision by the County administrative boards of Sweden (Länsstyrelsen). Because the Chief Guardian units lack a common governmental monitoring, internal solutions are created by every individual unit. In this qualitative study we have tried to understand how the social workers practise their profession. Through semi-structured interviews with eight social workers in three different Chief Guardian units, we have interpreted the views of their work. The theoretical framework was primarily founded on Polanyi´s theory of tacit knowledge and the ideas of occupational and organizational professionalism. The results of our study showed that the reality for the social workers is a mix of occupational and organizational professionalism. All the informants describe their work as heavily controlled by laws and regulations, but with a certain freedom of how to conduct their work. They find the tacit knowledge and the collegial support very important when it comes to assessing guardians. All the informants state that an organizational change is crucial to guarantee the legal security of guardians and caretakers.