> If it's not Canada's land then can I come in there and break laws and say Canadian law doesn't apply because it's not Canada?

There are 43 first nations communities in Canada that are entirely self-governing. The Canadian Police have no power and no jurisdiction, and the community deals with everything entirely itself.

So, yes, First Nations people in those communities break "Canadian" laws every single day and nothing "Canada" does nothing about it (and legally can't).

I don't know if that applies to you if you are not a first nations person of that community. I doubt it.

There are 25 self-government agreements across Canada involving 43 Indigenous communities

https://www.rcaanc-cirnac.gc.ca/eng/1100100032275/1529354547...