Here's the deal. The following Canadian territories were admitted to Canada under the following Acts:
- Manitoba Act 1870 and Rupert's Land Order
- British Columbia 1871 and Terms of Union Act
- Saskatchewan 1905 Saskatchewan Act and Constitution Act 1930
- Alberta Act 1905 and Constitution Act, 1930
From what I understand, NONE of these admittance acts prohibit separation from Canada. In Canada, its a real thing. These territories can separate. And, it is looking more and more like they will. If they do this, they will likely want to become territories of the United States by treaty. I wouldn't be surprised if Trump isn't having his team secretly meet with the heads of these territories to discuss this.