There is a narrow body of law dealing with (mostly trade) disputes (and since Trump's tariffs: 'co-operation') between various provinces, and sometimes the national government.
O. Reg. 287/25 - PUBLICATION AND REPORTING REQUIREMENTS
O. Reg. 286/25 - ADMINISTRATIVE PENALTIES
O. Reg. 199/25 - DEEMED CERTIFICATION
O. Reg. 505/10 - MONITORS FOR NON-GOVERNMENTAL REGULATORY AUTHORITIES