I can see it now. Nicotine sniffing dogs in airports and border crossings to make sure you're not smuggling vape products into the US.
Having crossed the border to and from Mexico literally hundreds of times for medical and dental treatment, I have observed CBP's "drug-sniffing dogs" over a 12 year period, and they are a sad hoax ...
The dogs used in the vehicle lanes are half-crazed by hours of breathing intense exhaust fumes, I've seen them go berserk and attack their handlers in an effort to escape ...
Indoors in the pedestrian lanes, the dogs are immersed in a combination of perfumes, body odor, and the reek of decaying facilities, compounded by industrial cleaning fluids and the stench of poorly maintained public restrooms ...
The worst example is when they assault women and girls at a certain time of the month. I could not think of a way to describe that more delicately ...
I'm certain that dogs can be trained to detect large volumes of illegal substances in controlled conditions. But a small quantity of nicotine in a closed container, in a malodorous environment ? Not a chance. The dogs can only reach most people below the knees, and if they try to climb higher, they are restrained immediately, to avoid a panic ...
So I suppose that its advisable not to carry "contraband" in your shoes ...
My sympathy is with the dogs, they didn't ask to be subjected to chaotic conditions and a constant assault on their senses ...