Provinces were allowed to override federal criminal law with respect to safe injection sites (federal police in canada were standing outside and arresting addicts as they came in/out)

Note, most local police in canada are federal.

The supreme court ruled that the provincial health concerns overrode federal criminal ones.

https://en.wikipedia.org/wiki/Canada_(AG)_v_PHS_Community_Se...

This sort of thing has a long history in Canada. Although in theory the federal government is much stronger than the USA federal government with respect to Provinces/States, the reality has played out significantly differently. Likely because of the influence of Quebec on canadian regional politics, and the fact there are fewer provinces than there are American states.