Grayscale Investments called the the U S. Securities and Exchange Commission’s (SEC) June decision to reject its application to convert its flagship Grayscale Bitcoin Trust (GBTC) into a spot bitcoin exchange traded fund (ETF) “arbitrary, capricious, and discriminatory” in an opening legal brief filed as part of its lawsuit against the regulator.

Grayscale filed suit against the SEC on June 29th, asking the U.S. Court of Appeals for the District of Columbia Circuit to review the regulator’s decision, which the SEC has published earlier in the day.

Grayscale is a wholly-owned subsidiary of Digital Currency Group, the parent company of CoinDesk.

Grayscale is far from the only company whose spot bitcoin ETF application has been rejected – over the last year, the SEC has denied over a dozen similar applications from other major players in the crypto space, including WisdomTree and Ark21Shares, citing a lack of investor protections and the potential for fraud and manipulation.

WisdomTree’s latest application was rejected the same day Grayscale filed its brief.

While the agency has repeatedly rejected bitcoin spot ETF applications, it has approved several bitcoin futures ETFs, making a distinction between the offerings that Grayscale’s lawyers say is “arbitrary” and “outside the Commission’s authority.”

In the brief, the attorneys argue that, because Bitcoin futures and spot Bitcoin both generate their price based on overlapping indices, the spot price of Bitcoin in both spot and futures ETFs are subject to the same risks – and therefore, approving one and denying another is unfair.

“The Administrative Procedure Act and Exchange Act require rules and regulations to be

applied without favoritism for one type of product or another,” said Craig Salm, Grayscale’s Chief Legal Officer, in a press statement.

The SEC’s response is due Nov. 9.