A quartet of lawsuits challenging in-house enforcement actions brought by the U.S. Securities and Exchange Commission became a quintet on Friday, signaling that it could take a federal appeals court—and maybe even the U.S. Supreme Court—to decide once and for all whether the SEC’s administrative proceedings pass muster.

The latest challenge came on Friday, in the form of a 16-page complaint filed in Manhattan U.S. district court by former Standard & Poor’s executive Barbara Duka. The lawsuit says the SEC is poised “imminently” to initiate an administrative case against Duka, who was previously cochief of S&P’s U.S. commercial mortgage-backed securities ratings business. Duka seeks an injunction blocking the SEC proceeding, as well as a judgment declaring all such proceedings illegal.