(Bloomberg) -- Gary Gensler’s push for the Securities and Exchange Commission to get tough on cryptocurrencies is drawing a rebuke from a key GOP lawmaker.

Senator Pat Toomey, the top Republican on the Senate Banking Committee, blasted Gensler for trying to regulate the digital-asset industry “by enforcement.” Toomey chided Gensler at a Tuesday hearing for not being more transparent about how the SEC determines whether a digital asset is a security that is subject to tough investor-protection rules. 

Gensler fired back: “I think there is a fair amount of clarity.” The SEC chief added that he’s “not negative or a minimalist when it comes to crypto, I just think it would be best if it was inside the investor-protection regime that Congress has laid out.”

Since taking over as SEC chief in April, Gensler has taken a hard line on crypto exchanges. He said Tuesday that there are only a “small number” of digital assets that don’t need to be registered with the SEC. Gensler added that stablecoins, a fast growing corner of the market, might well be securities. 

Crypto advocates have been frustrated by Genlser’s stance, particularly after Coinbase Global Inc. disclosed last week that the SEC had threatened to sue if the exchange launched a product that would let clients earn interest by lending their coins to other traders. 

The revelation triggered the same regulation-by-enforcement criticisms that Toomey flagged at the Senate committee hearing. 

“Why wait to make the SECs views known only when it swoops in with an enforcement action, in some cases years after the product was launched,” said Toomey. “It’s very objectionable.”

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