Canadian Border and Propane Tanks ON?

No such thing.

I don't know how many times we have crossed and propane has never been a question.

Canada requires propane be turned off on all ferries. Which is not a requirement in the US.

That has to be for the tunnel.

I've crossed many times in many places, and never been asked about propane. The did take my blueberries even though they were Canadian!

Hmmm. I wonder who would check it.

Have crossed many multiple times, been inspected 5 or 6 times, and never once have they even checked my propane.

They enforce smuggling, immigration, customs and excise tax, not transport of propane on an RV.

Of course, going through the Detroit/Windsor tunnel it is not allowed, but that isn't a Can/US customs regulation, its the tunnel owner.

Sure sounds like Eltoro poopoo to me.