NEW YORK ( TheStreet) -- When Morgan Sze decided to leave Goldman Sachs ( GS) last month, it wasn't just another hotshot trader leaving a big bank to start his own firm. It was the end of an era. Sze, who turned 45 in September, joined Goldman as an associate in 1993. By 2009, Sze had become the most valuable man at the most profitable firm on Wall Street, as head of the firm's proprietary trading group known as Goldman Sachs Principal Strategies. His salary range in recent years was exponentially higher than that of CEO Lloyd Blankfein. "He was a good trader -- he saw arbitrage, saw opportunities and was ready to take positions that others weren't," says a source who once worked at Goldman and knows Sze but wasn't willing to speak on the record due to business relationships. "He was paid based on a formula that makes total sense, but not in the current environment. Not at Goldman Sachs." Sze isn't leaving Goldman to launch his own hedge fund, called Azentus Capital, because of his ego or vengeful bosses jealous of his pay. He is leaving due to an 83-year-old economist named Paul Volcker. That's because a new law dubbed the "Volcker Rule" means Goldman can no longer be a home for traders like Sze, who once ruled the bank and Wall Street. Sze was a master of proprietary trading, which is when a firm makes large, often risky bets using in-house capital. Sze is just the last in a string of high-profile departures from Goldman Sachs Principal Strategies as a result of the Volcker Rule. GSPS, as it's commonly referred to, has now been dismantled, with all 70 of its employees leaving for opportunities at hedge funds, private-equity shops or other organizations that, unlike Goldman, aren't quite so heavily regulated. Among the other high-profile departures were Pierre-Henri Flamand, who preceded Sze as head of GSPS, and launched a hedge fund called Edoma Capital Partners last year; Daniele Benatoff and Ariel Roskis, from GSPS's European desk, who left to start a fund of funds to be financed by the large Swedish hedge fund firm Brummer & Partners; and another Goldman prop-trading pro, Bob Howard, who took a group of nine traders to private-equity firm KKR ( KKR).