Artikel 42

1. Law enforcement officers of States Parties who, within the framework of a criminal investigation, are keeping under observation in their country a person who is presumed to have taken part in a crime to which the State Parties concerned apply this Convention, or a person who it is strongly believed will lead to the identification or location of the former person, may be authorized to continue their observation in the territory of another State Party where the latter has authorized the cross-border observation in response to a request for assistance which has previously been submitted. Conditions may be attached to the authorization.
2. On request, the cross-border observation may be entrusted to officers of the State Party in whose territory it is carried out.
3. The request for assistance referred to in paragraph 1 shall be sent to an authority designated by each State Party and having jurisdiction to grant or to forward the requested authorization.
4. The cross-border observation, if carried out by one or more officers referred to in paragraph 1, shall be carried out only under the following general conditions:
a) The officers conducting the observation shall comply with the provisions of this article and with the domestic law of the State Party in whose territory they are operating; they shall follow the instructions of the competent authorities of that State Party;
b) The officers conducting the observation shall, during the observation, carry a document certifying that authorization has been granted;
c) The officers conducting the observation shall be able at all times to provide proof that they are acting in an official capacity;
d) The officers conducting the observation may carry their service weapons during the observation, unless specifically otherwise decided by the requested State Party; their use shall be prohibited save in cases of legitimate self-defense in accordance with the domestic law of the requested State Party;
e) Entry into private homes and places not accessible to the public shall be prohibited;
f) The officers conducting the observation may neither stop and question, nor arrest, the person under observation;
g) All operations shall be the subject of a report to the authorities of the State Party in whose territory they took place; the officers conducting the observation may be required to appear in person;
h) The authorities of the State Party from which the observing officers have come shall, when requested by the authorities of the State Party in whose territory the observation took place, assist the enquiry subsequent to the operation in which they took part, including any legal proceedings.
5. For the purposes of paragraph 3, each State Party shall indicate the competent authorities by informing the central authorities of the States Parties, or, if the conditions in article 85, paragraphs 2 and 3, are met, the State designated to provide additional interim support.