From the NDA
‘Placing forces on active service
- 31(1) The Governor in Council may place the Canadian Forces or any component, unit or other element thereof or any officer or non-commissioned member thereof on active service anywhere in or beyond Canada at any time when it appears advisable to do so
- (a) by reason of an emergency, for the defence of Canada;
- (b) in consequence of any action undertaken by Canada under the United Nations Charter; or
- (c) in consequence of any action undertaken by Canada under the North Atlantic Treaty, the North American Aerospace Defence Command Agreement or any other similar instrument to which Canada is a party.’
No legislative changes required, actually a fairly simple and easy process to enact. Again what is lacking is the will power to do so rather than any sort of law or legislation.