Rule of law as institutional substrate — contract enforcement, judicial independence, equal treatment before the law. Upstream of most other axes.
S.C. 2005 c.33 of 20 July 2005. Federal definition of civil marriage opened to same-sex couples following prior provincial appellate court rulings (Ontario, BC, Quebec 2003-2004) and Supreme Court Reference re Same-Sex Marriage 2004. Canada became 4th country globally to legalise same-sex marriage after Netherlands (2001), Belgium (2003), Spain (2005).
Per invariant 3, reforms are scored by what they did on each channel-separated axis, not by the party that enacted them. This fingerprint is how the policy-match engine finds historical analogues.
Explicit links are curated by the author. Inferred links are hypotheses in the library that test the same axes this policy moved — the framework's answer to "what does the data say about a policy like this?".
Ranked by axis-fingerprint overlap with this policy. Direction match bolded — those are the closest historical analogues. Shape of the match is what drives policy-outcome comparison, not the country or party label.