Sidley Austin on Tuesday vowed to fight claims that it, along with 18 other lawyers and law firms, helped to perpetuate a $1.3 billion Ponzi scheme that swindled money out of thousands of investors.

According to a $500 million lawsuit filed by the receiver who is representing the investors, Sidley and one of its attorneys, Neal Sullivan, were “heavily involved” in the legal matters of Woodbridge Group of Cos., which was led by California executive and incarcerated mastermind Robert Shapiro.