Securities and Exchange Commission Chair Gary Gensler has a warning about the synthetic stocks popping up on blockchains: Firms selling the tokens to U.S. investors are likely to end up in trouble with regulators.

In a Wednesday speech, Gensler made clear that tokens that mirror the performance of Amazon.com Inc., Tesla Inc. and other well-known companies are probably still covered by U.S. securities laws. He also pledged to use all the resources in the SEC’s “enforcement toolkit” to go after those who might be offering such assets without registering them.

“It doesn’t matter whether it’s a stock token, a stable value token backed by securities or any other virtual product that provides synthetic exposure to underlying securities,” Gensler said for an event held by the American Bar Association. “These platforms -- whether in the decentralized or centralized finance space -- are implicated by the securities laws and must work within our securities regime.”

Gensler’s comments referenced what’s known as DeFi, a fast-moving corner of the cryptocurrency market where tokens that track the performance of huge companies have started emerging. The trading has triggered regulatory scrutiny that’s prompted some in the industry to pull back. Cryptocurrency exchange Binance Holdings announced last week that it was phasing out support for tokens linked to equities.

Gensler has repeatedly said that cryptocurrencies need more oversight. In May, he told a House panel that he was looking forward to working with Congress and other regulators “to fill in the gaps of investor protection.” He added that digital token exchanges were ripe for additional rules and urged lawmakers to pass legislation giving the SEC authority to police the trading venues.