The proper Vantablack coatings are ITAR restricted materials that require an export license, so the comparison is really quite meaningful. You wouldn't be killed for using it without the King's permission, but you could serve time at His Majesty's pleasure for it.

https://www.surreynanosystems.com/purchasing

You could always get the much cheaper and easier to buy Black 3.0 or 4.0

https://www.culturehustleusa.com/products/black-4-0

Also it wouldn't stick to a cloak, it would most likely rub off.

Not the police and not vantablack, but don't try certain football team colors on certain other teams' stadiums

I wonder if future people will compare trademark law to sumptuary laws. It being illegal to distribute fake Gucci might be seen like that.

we should bring back sumptuary laws, can make it legal by prohibiting the sale of some materials to nonaccredited investors with the consequences of unlimited tax to the business

circumvents freedom of expression by giving no consequences to the individual if they someone procure the material themselves

but leverages the unlimited right to regulate commerce and unlimited right to tax