Section 156 states:
156. Such officers and non-commissioned members as are appointed under regulations for the purposes of this section may
a) detain or arrest without a warrant any person who is subject to the Code of Service Discipline, regardless of the rank or status of that person, who has committed, is found committing, is believed on reasonable grounds to have committed a service offence or who is charged with having committed a service offence;
b) exercise such other powers for carrying out the Code of Service Discipline as are prescribed in regulations made by the Governor in Council.
QR&O 22.02(2) spells out who is included in section 156:
The following persons are appointed for the purposes of section 156 of the National Defence Act:
a) every officer posted to an established position to be employed on military police duties, and
b) every person posted to an established military police position and qualified in the military police trade, provided that such officer or person is in lawful possession of a Military Police Badge and an official Military Police Identification Card.
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Military police personnel are "specially appointed persons" under section 156 of the National Defence Act.10 As such they have the power to arrest,11 investigate,12 and use force in certain circumstances.13 Military Police do not, however, have the power to lay charges (even charges for criminal offences) under the Code of Service Discipline.14 Only an officer or non-commissioned member authorized by a commanding officer to lay charges can lay a charge.15
Military Police personnel are also "peace officers"16 under section 2 of the Criminal Code. Section 2 defines peace officers to include officers and noncommissioned members of the CF appointed for purposes of section 156 of the National Defence Act. The definition also includes any officer or noncommissioned member performing duties prescribed by the Governor in Council as being of such a kind that they "necessitate" the person having peace officer powers. In the QR&O,17 the Governor in Council prescribes the duties that necessitate peace officer powers as any lawful duties performed as a result of a specific order or established military custom or practice related to any of the following:
the maintenance or restoration of law and order;
the protection of property;
the protection of persons;
the arrest or custody of persons; or
the apprehension of persons who have escaped from lawful custody or confinement.
When acting as peace officers, military police have the powers of arrest set out in section 495 of the Criminal Code.18 They can also lay charges in civil courts without the concurrence of the commanding officer.
The Security Orders for the Department of National Defence and the Canadian Forces describe the jurisdiction of the Military Police as follows:
MP are the primary police force of jurisdiction and exercise police authority with respect to:
persons subject to the Code of Service Discipline, without regard to their rank, status or location; and
any other person, including civilian employees, dependants, visitors or trespassers, in regard to an event, incident or offence, real or alleged, which occurs or may occur on or in respect to defence establishments, defence works, defence materiel or authorized Canadian Forces programmes, activities or operations.
Prior to exercising police authority off a defence establishment, MP must first satisfy themselves that some other police agency does not have a right of primary jurisdiction. A connection, or nexus, to the Service is an essential prerequisite. In the absence of such a nexus, police authority should only be exercised by MP with the concurrence of the appropriate civil authority. Police authority is clearly distinct from the implicit duties and responsibilities of any good citizen.
Where an offence has been committed in Canada by a person subject to the Code of Service Discipline outside of a defence establishment, the matter should be dealt with by the appropriate civilian authorities, unless a Service connection, or nexus, is apparent. In these latter cases, the matter may be considered a Service offence and dealt with accordingly.