France’s stock market regulator announced on Thursday that it has blacklisted 15 cryptocurrency and crypto-asset investment websites.

The Autorite des Marches Financiers (AMF) will add the offending platforms to its existing “liste noir,” which already includes businesses that unlawfully offer investments in commodities like diamonds, rare earth metals and wine.

The announcement explained:

“Companies in France offering the purchase of rights over goods promoting the possibility of a yield or its economic equivalent are subject to the regulation of diverse goods and as such their offer must have a registration number provided by the AMF.”

The announcement goes on to list the websites of fifteen companies who have been alerted by the AMF of their regulatory violations but continue to operate. The majority of those on the list claim to be located in the U.K.

Among them is AKJ Crypto, which claims to provide a variety of services ranging from asset storage to account management. Another, Crypteo, is a purported cryptocurrency marketplace.

The AMF’s statement cautioned investors that “no sales pitch should make one forget that there are no high returns without high risks.” Likewise, it advised them to perform due diligence on the investments they’re considering and to weigh the criteria used to establish a product’s price.

The regulator also said that investors should consider the means by which a product can be resold and the deadlines which may correspond to this.

“Don’t invest in that which you don’t understand,” the Authority cautioned.

This is not the first time the AMF has involved itself in the affairs of the crypto industry. In February, it released a statement positing that trading platforms should not be allowed to market cryptocurrency derivative products electronically because they fall within the realm of the MiFID 2 and Sapin 2 laws, the latter of which bans advertisements for certain financial contracts.

Likewise, the Authority launched the Universal Node to ICO Research Network (UNICORN) in October of 2017. At the time, it described the program as providing a framework that would allow ICO issuers to develop their operations while ensuring the protection of would-be investors.

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