• Registered securities firm Prometheum intends to take custody of customers' UNI and ARB as securities when it gets rolling, adding them to its existing plans for Ethereum's ether.
• While the crypto industry fights the Securities and Exchange Commission's stance on tokens as securities, Prometheum is still seeking a road to comply with the agency's view.
• The company intends to open its custodial doors in earnest in September.

Prometheum is forging ahead with its strategy to comply with the U.S. Securities and Exchange Commission's view on cryptocurrency transactions by letting two more tokens into its custody operation for crypto securities, whether the rest of the industry agrees or not.

The U.S. firm's custodial business will accept tokens issued by Uniswap (UNI) and Arbitrum (ARB) in addition to its earlier announcement it would custody Etherium's ether (ETH) , company officials told CoinDesk. Treating these tokens as securities is meant to put Prometheum in line with what the SEC insists is the law for U.S. digital assets transactions: that the vast majority of tokens should be treated as securities under the agency's jurisdiction.

"Prometheum Capital views the federal securities laws as the regulatory framework that provides established, tried, and tested investor protections," said Benjamin Kaplan, CEO of subsidiary Prometheum Capital, in an emailed response to questions. "Providing a regulated mechanism to allow investors to responsibly participate in the digital asset space has always been our goal."

As the firm moves toward fully opening its doors to institutional customers by the end of next month, according to its own estimate, much of the industry is battling the SEC in federal courts. Some of the most prominent U.S. crypto firms are arguing (with occasional success ) that digital assets shouldn't necessarily be treated as investment contracts that count as securities. Bitcoin (BTC) is well-established as a commodity, for instance, which leaves it outside the SEC's reach.

Prometheum is a unique creature in the industry, because it's the first and only company to set up formally as a special-purpose broker-dealer for crypto assets. It's registered as a custodian and to clear and settle digital asset trades. Company officials' past predictions for when it would become a one-stop shop for crypto transactions have proven overly optimistic , and Kaplan is now only willing to say that'll happen sometime "after the full launch of its custodial offering."

The company's stance that the SEC is correct puts it at odds with most of its counterparts in the sector. SEC Chair Gary Gensler has more than once referred to the company as a potential example of crypto done correctly. So far, the regulator hasn't openly pushed back on Prometheum's business model, but the firm has only proceeded to date with a "soft launch" in May, though Kaplan wouldn't offer details about what that meant and whether the company is earning revenue.

He also declined to say whether the company has received any reinforcement from the SEC about its business model, only that it engages with the regulator "in the normal course of business."

If institutional customers do knock on its door later this year, the company contends that the type of blockchain-backed custody it's offering is more transparent and saves the costs of intermediaries, such as transfer agents.

Its earlier announcement about custodying ETH for clients raised questions among some of the company's critics , and Commodity Futures Trading Commission Chairman Rostin Behnam acknowledged in a congressional hearing that a securities firm handling ETH could run afoul of his agency's decision to treat that token as a commodity.

The SEC has signaled that UNI may be a security, as well, when it threatened an enforcement action . Uniswap Labs contends the arguments for UNI being a security are unfounded.

"The SEC’s aggressive theories are an effort to expand its jurisdiction beyond exchanges to communications technology – and beyond securities to all markets. Their legal arguments are weak and have been refuted by courts," the Uniswap Labs argued in a May blog post .

ARB is the native token of the Arbitrum network , billed as a faster and cheaper blockchain for transacting on Ethereum.

When asked why Prometheum selected UNI and ARB, Kaplan responded, "Prometheum Capital intends to provide investors access to the top digital assets over time, as well as tokenized assets, debt, equities, [exchange traded funds], mutual funds, options, money market funds and other investment contract products that are issued and transferred on a blockchain."

Read More: Prometheum, the Only U.S.-Registered Crypto Platform, Picks Ether as Its First Product