Some information from the Customs Act and the Customs Tariff:
Customs Act. s.35.01
Marking of Goods
Marginal note:Requirement to comply with marking regulations
35.01 No person shall import goods that are required to be marked by any regulations made under section 19 of the Customs Tariff unless the goods are marked in accordance with those regulations.
1993, c. 44, s. 83;
1997, c. 36, s. 155.
35.02 (1) [Repealed, 2001, c. 25, s. 30]
Marginal note:Notice requiring marking or compliance
(2) The Minister or any officer designated by the President for the purposes of this section may, by notice served personally or by registered mail, require any person
(a) to mark imported goods in accordance with the regulations made under section 19 of the Customs Tariff, within such reasonable time as may be stipulated in the notice, if there has been a failure to comply with section 35.01 with respect to the goods; or
(b) to comply with section 35.01 in respect of any goods designated in the notice that will subsequently be imported by the person.
Customs Tarrif s.19
Marking of Goods
Marginal note:Regulations requiring marking
19 (1) The Governor in Council may, on the recommendation of the Minister, make regulations
(a) requiring imported goods of any description or class, including a description or class specified in terms of the use of the goods, to be marked, in accordance with regulations made under subsection (2), so as to indicate their country or geographic area of origin; and
(b) for determining the country or geographic area of origin of imported goods for marking purposes.
Marginal note:Regulations prescribing marking requirements
(2) The Minister of Public Safety and Emergency Preparedness may make regulations for the purpose of the administration of this section, including regulations prescribing
(a) the manner in which imported goods must be marked and any conditions applicable to the marking of the goods; and
(b) when imported goods must be marked, including whether they must be marked before or after importation, and any conditions applicable to the time of marking.
Marginal note:Applicability of regulations
(3) Regulations made under this section may apply generally or be limited to particular countries or geographic areas defined in the regulations.
According to this, CBSA can require marking post-importation and can enforce the same if they so choose.