The Commodity Futures Trading Commission conceded defeat in one of its hardest-fought legal battles, saying it would not appeal a federal court ruling that threw out its market manipulation case against a prominent Chicago trader.

After “careful consideration,” CFTC Chairman J. Christopher Giancarlo decided not to appeal the November 30 verdict dismissing the regulator’s lawsuit against Donald Wilson Jr. and his firm, DRW Investments, a commission spokeswoman said in a statement.