Real estate developer Donald Trump displays his hairline after a luncheon speech at the National Press Club in Washington on May 27. Reuters/Gary Cameron A civil racketeering lawsuit against Donald Trump can proceed as a class action, a federal judge has ruled, in a major incremental victory for a former student accusing him of running a bogus investment university.

The ruling by Judge Gonzalo Curiel means that a California businessman named Art Cohen can sue Donald Trump on behalf of anybody who bought seminars from Trump University after January 2007.

That lawsuit accuses Donald Trump and his university of violating federal racketeering law by scheming to defraud students into paying thousands of dollars for useless real estate investing classes.

Curiel's ruling is a big deal because it is generally not worth a lawyer's time to pursue a case like this on behalf of one person. Now, Cohen is representing thousands of people who were allegedly duped by Trump University, according to court documents filed by his attorneys.

Here's what Trump's lawyers said in a statement emailed to Business Insider: "We are taking action to immediately appeal the Court’s decision to certify a class in this case. However, we are confident that Mr. Trump will ultimately prevail on the merits once all the evidence is considered."

Trump University stopped operating in 2011 but has been the subject of continuous litigation. New York Attorney General Eric Schneiderman sued Trump University last year for allegedly failing to deliver on promises to teach real estate investment techniques and defrauding students of $40 million.

Cohen also filed his suit last year after he allegedly spent $34,996 on Trump University's "Gold Elite" program. Trump misled students into believing they would learn investment secrets from both him and his "handpicked professors," the lawsuit claims. Instead, Cohen said, Trump had no real role in choosing instructors and didn't give students access to any of his real estate investing secrets.

"The misleading nature of the enterprise is embodied by its very name," the complaint said. "That is because, though Defendant promised 'Trump University,' he delivered neither Donald Trump nor a university."