If not for banker Bradley Birkenfeld, “a massive tax fraud scheme” by Switzerland’s UBS bank to hide the assets of wealthy Americans from U.S. tax collectors would never have been uncovered, prosecutors told a Fort Lauderdale, Fla., federal judge.

Birkenfeld’s attorney said his client is responsible for revamping international banking laws to make it easier to prosecute people who squirrel away money in foreign tax havens.