@Mushroom
I have no idea why you think it would be illegal to use them
Because most historically used dyes needed mordants to bind them to the fibre.(bold set by me)
Many natural dyes require the use of substances called mordants to bind the dye to the textile fibres. Mordants (from the Latin verb 'mordere', meaning 'to bite') are metal salts that can form a stable molecular coordination complex with both natural dyes and natural fibres. Historically, the most common mordants were alum (potassium aluminum sulphate - a metal salt of aluminum) and iron (ferrous sulphate). Many other metal salt mordants were also used, but are seldom used now due to modern research evidence of their extreme toxicity either to human health, ecological health, or both. These include salts of metals such as chrome, copper, tin, lead, and others.
Using different mordants with the same dye results in different colour shades e.g. yellow, orange, brown.
You write:
But all using old style fabrics and natural authentic dyes to the era.
They are also often used for those with allergies. My uncle before he died got most of his shirts from a company here in Oregon that only used 100% natural plants, all found in the local area
That's bullshit. Just because it's natural doesn't mean it's healthy! Ever tried to eat Amanita phalloides aka death cap?
While historically, dyers possessed sophisticated knowledge of natural sources of true dye compounds, nowadays the internet contains a lot of inaccurate information about sources - predominantly foods - that are not supported by the historic record or by modern science. In natural dyeing, there are 'fast' dye compounds (those that have the necessary molecular structure to form stable chemical bonds with mordants and fibres, and so provide good resistance to fading when washed, exposed to light, or subjected to normal rubbing/abrasion; these are found throughout the historic record), and there are 'fugitive' compounds, which are not true dyes (those that fade and wash out quickly, as they lack the molecular structure to form stable bonds, or any bonds at all, to mordants and fibres). Mordanting can not fix fugitive sources to fibres. Fugitive sources include nearly all berries, red cabbage, beets, spinach, black beans, most flowers (though some important true dyes are flower derived) and many others.
I looked at the link you provided and I guess all their dyes are 'fugitive'. One colour baffled me: black indigo.
Indigo is blue, never black!
HM.