It is common enough for various jurisdictions to forbid discrimination on the basis of national origin.
Do such prohibitions cover discrimination on the basis of sub-national origin?
For example, would it be permitted for a restaurant to serve all Canadians, except those from the province of Prince Edward Island?
In most countries, protections against discrimination are related to discrimination over the membership in a protected class. These would be enumerated in a law somewhere. For instance, Article 3 Section (3) of the Basic Law of Germany states
No person shall be favoured or disfavoured because of sex, parentage, race, language, homeland and origin, faith or religious or political opinions. No person shall be disfavoured because of disability.
The original text is German, of course, and what is translated 'parentage' here uses a German word which also implies 'descent.' The words which are translated 'homeland and origin' have geographic connotations, but not necessarily national ones.
On the other hand, it is clear that e.g. the Catholic Church will hire only practicing Catholics as priests. If they are free to hire only practicing Catholics as janitors is a more thorny question. And a state within Germany is allowed to favor citizens living in that state over those from other states for some purposes, but not others.
If the restaurant example was set in Germany, this would probably violate the 'homeland and origin' protected group and hence be illegal.
The human rights codes and constitutional instruments protect against discrimination on the basis of:
Your question is whether any of these have been interpreted to prohibit discrimination on the basis of province of origin.
Multiple human-rights bodies have interpreted their enabling legislation to not include province of residence as a ground of discrimination.
E.g. Dobbin v. Canada (Department of Fisheries and Oceans), 2005 FC 1020; Gardezi v. Insurance Corporation of British Columbia, 2010 BCHRT 262; Re Algonquin College and Ontario Public Service Employees' Union, 1985 CanLII 5355 (ON LA); Peplinski (Re), 2018 ONMIC 12 (CanLII): "Place of origin does not mean province of residence."
The Supreme Court of Canada has held that province or place of residence is not a ground of discrimimation under the Charter (Siemens v. Manitoba (Attorney General), [2003] 1 S.C.R. 6).
At least some of the plain wording in some of the relevant instruments appears to potentially prohibit discrimination on the basis of province of origin. E.g. those that prohibit discrimination on the basis of "place of origin," as opposed to more specifically "national origin."
The BC Human Rights Tribunal explain though that "Place of origin includes the fact of being born in a particular country or group of countries or region of Canada or the world."
I have found no reported judgment or decision of a human rights tribunal that has recognized discrimination on the basis of province of origin.
Province of origin has likely not been understood to be within the umbrella of "place of origin" because the grounds of prohibited discrimination are based on a history of disadvantage and historic patterns of discrimination. The Supreme Court of Canada has recognized that the purpose of protecting against certain grounds of discrimination is to "remedy or prevent discrimination against groups subject to stereotyping, historical disadvantage and political and social prejudice in Canadian society" (R. v. Swain, [1991] 1 S.C.R. 933). They "identify a basis for stereotypical decision-making or a group that has historically suffered discrimination."
In rejecting place of residence as a potential ground, the Supreme Court of Canada said:
Nothing suggests that Winkler [a city in Manitoba] residents are historically disadvantaged or that they suffer from any sort of prejudice.
A similar analysis may very well apply to an attempt to claim province of origin as a ground of prohibited discrimination. But it is of course open for someone to argue with evidence in an appropriate case.
In the US, this would fall under the Privileges and Immunities Clause of the Constitution:
The Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States.
This has generally been recognized as a bar on restricting the rights of out-of-state citizens, but the exact meaning of the clause isn't always the most clear. In the 1869 case Paul v. Virginia, the Supreme Court clarified (emphasis mine):
It was undoubtedly the object of the clause in question to place the citizens of each State upon the same footing with citizens of other States, so far as the advantages resulting from citizenship in those States are concerned. It relieves them from the disabilities of alienage in other States; it inhibits discriminating legislation against them by other States; it gives them the right of free ingress into other States, and egress from them; it insures to them in other States the same freedom possessed by the citizens of those States in the acquisition and enjoyment of property and in the pursuit of happiness; and it secures to them in other States the equal protection of their laws.
It is unconstitutional for a state to either directly discriminate against non-residents, or for state law to allow residents to do it, assuming that residents are not equally impacted. (For instance, a business offering free shipping within a 100-mile radius would be permitted, as non-residents and residents who happen to be outside the radius are treated the same.)
As with all US discrimination law, there are sometimes exceptions carved out when there is a rational basis to do so. For example, state universities traditionally offer greatly reduced tuition to state residents, the theory being that state residents pay state taxes which fund state universities, so they have in effect already paid part of their share.
