4 (1) Subject to section 5, the Registrar shall attach to a registration certificate that is issued in respect of a firearm the condition that the holder of the certificate shall advise the Registrar, within 30 days after the modification, of
(a) any modification to the firearm that results in a change of class of the firearm;
(b) in the case of a firearm registered as a frame or receiver only, any modification that makes it capable of discharging ammunition;
(c) any modification to an altered automatic firearm; and
(d) any modification that results in the firearm ceasing to be a firearm.
(2) Subject to section 5, the Registrar shall attach to a registration certificate that is issued in respect of a firearm the condition that when the type, action, calibre or gauge of the firearm is modified, the holder of the certificate shall advise the Registrar of the modification,
(a) if the modification is intended to be permanent, within 30 days after the modification; and
(b) if the modification is not intended to be permanent but still exists 30 days after it is made, without delay after that period.
SOR/2004-276, s. 4
<https://laws-lois.justice.gc.ca/eng/regulations/SOR-98-201/page-1.html#h-1019122>