With a veto override vote scheduled for Wednesday in the Senate, Defense Secretary Ash Carter is doing some last minute public lobbying against the Justice Against Sponsors of Terrorism Act (JASTA), which previously passed unanimously in both the House and Senate.

JASTA would allow the families of victims of the 9/11 attacks to sue Saudi Arabia for its role in supporting plotters in the lead-up to the attack. President Obama vetoed the bill Friday, claiming other nations could reciprocate and that it would open taxpayers up to lawsuits for America’s own misdeeds internationally.

Carter’s opposition to JASTA took a different tack, arguing that a lawsuit against Saudi Arabia over 9/11 would lead to “an intrusive discovery process,” and ultimately lead to the public disclosure of “American secrets,” potentially damaging the terror war.

While this is in keeping with the administration’s obsession to keep myriad secrets (after all, the 28 pages disclosure on Saudi involvement in 9/11 only became public in a heavily redacted form after a protracted effort), it also seems to amount to an admission that America has more secrets that would be relevant in the case against the Saudis.

Exactly what that would be, or even where it would come from, is unclear, as while there were considerable redactions within the 28 pages, none of them gave the appearance of providing any US ties to any of the pre-9/11 shenanigans.

The Senate’s vote will be Wednesday on the override, and assuming it passes the House is expected to vote later in the week. The House is widely assumed to have the votes, while the Senate is expected to be closer, though advocates in both parties have suggested they believe they can override the veto. Those wishing to contact their senators at the last minute in support of JASTA can find contact information here.