Der skal altså finde en afvejning sted mellem en krænkelse af privatsfæren og det formål, det handler om. Det skal være forudsigeligt, det vil sige, at borgerne skal vide, at der findes et sådant system.
Briefly, the conditions are as follows: there must be a legal basis for such an operation - it cannot be arbitrary; a value judgment must be made, the breach of privacy being weighed against the morality of its purpose; the operation must be foreseeable, which means that the general public must know that such a system exists, and recourse to interception must only be permitted if there is no alternative.