Since the transposition of the EIO Directive the cross-border observation may be applied on the basis of the EIO under the condition that there is a prior agreement between the Polish Police/other LEA and the competent authority of the issuing Member State, which enables a Polish prosecutor to confirm such EIO issued by the Polish Police/other LEA, or to issue a decision on executing such EIO issued by the competent authority of another EU Member State.
Otherwise, usually with neighbouring countries this measure is applied as a form of a Police-to-Police cooperation and then the cross-border observation of persons is not considered as a form of judicial assistance and hence no involvement of judicial authorities (in Poland a court or a prosecutor) is envisaged. Police/other LEA may cooperate in cross-border observation provided that Poland is a party to certain international agreements. Such agreements include: Convention implementing the Schengen Agreement of 1990 (CISA) and bilateral instruments with neighbouring countries, like Germany, Lithuania, Slovakia.