Section 95(1) criminal code:

ossession of prohibited or restricted firearm with ammunition
95. (1) Subject to subsection (3), every person commits an offence who, in any place, possesses a loaded prohibited firearm or restricted firearm, or an unloaded prohibited firearm or restricted firearm together with readily accessible ammunition that is capable of being discharged in the firearm, unless the person is the holder of
(a) an authorization or a licence under which the person may possess the firearm in that place; and
(b) the registration certificate for the firearm.
Punishment
(2) Every person who commits an offence under subsection (1)
(a) is guilty of an indictable offence and liable to imprisonment for a term not exceeding 10 years and to a minimum punishment of imprisonment for a term of
(i) in the case of a first offence, three years, and
(ii) in the case of a second or subsequent offence, five years; or
(b) is guilty of an offence punishable on summary conviction and liable to imprisonment for a term not exceeding one year."
And the firearm act:
Places where prohibited and restricted firearms may be possessed
17. Subject to sections 19 and 20, a prohibited firearm or restricted firearm, the holder of the registration certificate for which is an individual, may be possessed only at the dwelling-house of the individual, as recorded in the Canadian Firearms Registry, or at a place authorized by a chief firearms officer.
1995, c. 39, s. 17; 2003, c. 8, s. 15.
AND FINALLY your backyard is not your dwelling. You need permission from the CFO to possess it in your backyard before you can discharge there.