We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Adrian
saying something like:

I said a few days ago - there is no law against snow chains

There is if they may damage the road surface - which they can and will on
tarmac.

Which is the same as the general prohibition against damaging it with
tracked vehicles, etc, isn't it? Are snow chains mentioned specifically?