Yes common-law marriages are defined by law. State law in the US, provincial law in Canada.
In British Columbia, since 2013, a couple that has lived together 2 years or more is considered married common-law. They have the same rights as married couples when it comes to spousal support, property and inheritance rights.
In Alberta it’s known as an Adult Interdependent relationship and is governed by the ADULT INTERDEPENDENT RELATIONSHIPS ACT.
it’s three years or more or you have a child. No property rights but they have inheritance rights.
Saskatchewan has 2 years as the milestone and you have the same rights upon dissolution of the relationship as you would have if you’d gone through a ceremony.
Manitoba, 3 years, fewer if you have a child. You can register your common-law union with Vital Statistics. If you do and you break up you must register the dissolution of the union with V.S. or you can’t get married again. Same property rights as married.
Ontario, 3 years, fewer if you have a child and have cohabited with some permanence. No inheritance or property rights, they take out of the relationship what they brought into it or what they jointly acquired.
Quebec doesn’t recognize common-law relationships. No rights whatsoever.
New Brunswick, 3 years, 1 if you have a child. Rights to child and spousal support but no property or inheritance rights.
Nova Scotia 2 years together gives you the right to spousal support. No property or inheritance rights. BUT, register your common-law marriage as a domestic partnership with Vital Statistics and you acquire the same rights as a married couple.
Prince Edward Island, 3 years together or have a child. Spousal support but no inheritance or property rights.
Newfoundland and Labrador, 2 years. Spousal support but no inheritance or property rights.