| | Re: How to find out if this is legal?
I'm almost 100% sure it is illegal in Ontario to smoke in a vehicle with kids. I have heard it several times, but have not actually confirmed this. Don't know what province you're in, though.
Even if this is the case, I don't believe it would be the same within your own house. You may want to look into that, though.
However if you can prove they do it in their car with the kids, you might be on to something.