It is provided a method for controlling access to a physical space. The method is performed in an access control device and comprises the steps of: communicating with an electronic key to obtain an identity of the electronic key; obtaining a plurality of delegations; determining, from one of the delegations, that there is an auxiliary condition, wherein the auxiliary condition is that access is approved for the electronic key by an auxiliary party, authenticated by a digital signature by the auxiliary party; and granting access to the physical space when the plurality of delegations comprises a sequence of delegations covering a delegation path from the access control device to the electronic key such that, in the sequence of delegations, the delegator of the first delegation is the access control device, the receiver of the last delegation is the electronic key, and the auxiliary condition is fulfilled.