husband cannot become canadian national "automatically" in Canada. First,he will have to submit the application for the residency (way before becoming canadian citizen), and to go through the immigration process, to get checked 100 times for Security reason, and such.. and - moreover - his application might be rejected. Once approved, he will have to live in canada 3 year continuously, then to apply for the citizenship, and to attend a citizenship test. Citizenship also can be denied or postponed depends on circumstances. Each country has rights to protect their interests the way they want.

as for nigerians in qatar, it is simply a matter of Work visa restrictions for nigerians. And again, each country has rights to protect their interests the way they want.

BTW, here an article about Algerians

http://new.arabianbusiness.com/qatar-cracks-down-on-algerian-visa-applicants-416509.html