Article 1E of the 1951 Refugee Convention states:

This Convention shall not apply to a person who is recognized by the competent authorities of the country in which he has taken residence as having the rights and obligations which are attached to the possession of the nationality of that country.

The leading case for interpreting Article 1E is Canada (Citizenship and Immigration) v. Zeng, 2010 FCA 118.  There, the Federal Court of Appeal stated:

Considering all relevant factors to the date of the hearing, does the claimant have status, substantially similar to that of its nationals, in the third country? If the answer is yes, the claimant is excluded. If the answer is no, the next question is whether the claimant previously had such status and lost it, or had access to such status and failed to acquire it. If the answer is no, the claimant is not excluded under Article 1E. If the answer is yes, the RPD must consider and balance various factors. These include, but are not limited to, the reason for the loss of status (voluntary or involuntary), whether the claimant could return to the third country, the risk the claimant would face in the home country, Canada’s international obligations, and any other relevant facts.

In Desir v. Canada (Citizenship and Immigration), 2019 FC 1164, the Federal Court stated that the burden is on the Minister of Citizenship and Immigration to establish a prima facie case that a claimant holds or held status substantially similar to that of nationals in a third country before being able to invoke Article 1E.  The Court also found that a claimant’s choice to allow his or her status in a third country to expire amounts to an impermissible form of asylum shopping.