Such a moment would not be occurring had the Gallente Government had the due diligence and good faith to prevent Leopold from disappearing in the first place. If you truly value preventing tension and smoothing things over, I would have expected Gallente forces, capsuleer or not, to have attempted to extradite the criminal from the Wildlands already.
The fact that the Caldari State has made concerted efforts to hunt down our own traitor and the Gallente seemingly haven’t made a single modicum of effort to find theirs, which appears quite guilty and responsible of collaborating with Esri, or even being the cause of her defection is incredibly troubling.
At best it shows no interest from your Federation in behaving with good faith and at worst in certain lenses it makes the Federation look intentionally negligent and an accomplice of the Guristas Pirates for the sole purpose of damaging the Caldari State. At which point all out war is firmly inevitable.
If you truly want to undo this tension, your forces will bring Leopold in and allow the State Navy to interrogate him and then face the court issued punishment he deserves.