A federal judge in Washington, D.C., on Monday pressed lawyers for Binance, the world’s largest cryptocurrency exchange, to defend its request that she dismiss a high-profile case brought against it by the U.S. Securities and Exchange Commission (SEC). Binance has asked federal Judge Amy Berman Jackson to toss out a lawsuit the SEC filed alleging Binance broke its rules and committed fraud. The lawsuit is one of Binance’s last major legal challenges in the U.S. The SEC in June accused Binance, its then-CEO Changpeng Zhao and the exchange’s U.S. arm of artificially inflating its trading volumes, diverting customer funds, failing to restrict U.S. customers from its platform and misleading investors about its market surveillance controls. The regulator also accused Binance of unlawfully facilitating trading of several crypto tokens the SEC deemed unregistered securities. At the outset of Monday’s hearing, the judge quizzed lawyers for Binance over a core argument they have made for dismissal: that the SEC has no authority to regulate the crypto assets at issue because they do not meet the definition of investment contract. The Securities Act of 1933 outlined a definition of the term ‘security,’ yet many experts rely on a U.S. Supreme Court case to determine if an investment product constitutes a security. A key test is whether people are contracting to invest in a common enterprise with the expectation of profit. Jackson asked lawyers for Binance how she should square their argument that the crypto sector needs new regulation with existing case law indicating securities laws are designed to be flexible and protect investors. Monday’s hearing is the second closely-watched courtroom battle in a matter of days in which the SEC, the top U.S. markets regulator, has to defend its authority to regulate the crypto sector. Last week, Coinbase and the SEC locked horns over similar issues. The SEC’s case against Binance differs from the one against its rival Coinbase as it also includes allegations of fraud and market manipulation. Last year, Binance agreed to pay $4.3 billion to settle with the Department of Justice and the Commodity Futures Trading Commission over illicit finance breaches. Zhao pleaded guilty to breaking U.S. anti-money-laundering laws and agreed to step down as CEO, but the SEC’s case is still hanging over the exchange.