A method for constraining the extragalactic background light (EBL) has been developed previously by the authors. This involves extrapolating the Large Area Telescope (LAT) spectrum of a blazar into the TeV energy range and using this as the upper limit for the intrinsic blazar spectrum. A comparison of this extrapolation with the observed very-high energy (VHE) spectrum for the source gives an upper limit on the EBL absorption optical depth. We update this technique to include a possible contribution from electron-positron cascades and a rigorous error analysis. This technique is then applied to several TeV BL Lacs to provide strong upper limits on the EBL absorption optical depth.