This paper analyses issues which have occurred in the implementation of administrative court supervision over administrative acts of regulatory agencies. Here, this is HANFE when it implements supervision in proceedings for taking over joint stock companies, in particular, in proceedings when it establishes common activity. Firstly, the position of HANFE is examined as an independent regulatory agency and its powers over its addressees, in particular in the proceedings for taking over joint stock companies. The fundamental characteristics of the institute of common activity are also examined. If HANFE establishes that people are acting together and have overstepped the so called control threshold in a particular company, HANFE reaches a solution which forces persons who act together to make public the takeover-bid offer to other joint –stock companies. In these cases, the main supervisory task of HANFE comes to the fore given that it directly protects investors’ interests in the capital market. The legitimate interest is in being offered under market conditions to “exit” from the particular company at that moment when someone else gains control over them. For the persons who act together, the solutions which establish common activity and demand the obligation of making public takeover bids are most often are quashed in the event of an administration dispute. In these disputes some issues are contentious. These are the issue of local court supervision given the large number of first instance administrative courts and the issue of the distinctions between administrative court examination of the administrative act of HANFE and the question of whether the administrative court can and under what conditions resolve a dispute as a full jurisdiction dispute, or meritoriously resolve the case itself. The consequences for a regulatory body if its decision in administrative dispute is revoked and returned for re-trial and does not bring a new single act or brings a decision contrary to the legal understanding of the administrative court are also examined.