 WASHINGTON When big businesses like Shake Shack and the Los Angeles Lakers basketball franchise took millions of dollars worth of emergency loans intended for small businesses, Treasury Secretary Steven Mnuchin called such borrowing outrageous, narrowed eligibility and threatened to hold companies criminally liable if they did not give the money back. But in the last month, large companies have continued to take out big loans through the Paycheck Protection Program, including publicly traded firms with ready access to other forms of capital. That is posing a critical test for Mnuchin, who had set a Thursday deadline for firms that did not need the money or had other ways of obtaining capital to return their loans or face a government review and potential legal repercussions. Mnuchins threat is likely to set off a wave of new government audits and legal fights over who is entitled to money that was meant to keep small businesses afloat during the pandemic. Late on Wednesday, the Treasury extended the deadline, for a second time, to May 18. Ive spent the better part of the last two weeks talking with clients about whether or not to return the funds, said Paul Pollock, a lawyer at Crowell Moring who has been advising about 100 companies on their loans. Suddenly everybody needed to re-evaluate whether they met the eligibility requirements. That decision has been complicated by a series of rule changes enacted by the Treasury Department in the weeks since the program began. The new guidelines are intended to make it harder for big companies to qualify for loans but have been criticized for cutting off funds to companies that need money and have no other government help available to them. In a last-minute twist Wednesday, the Treasury said that loans for less than 2 million would be... 