The problem with giving away the assets, and I’m just parroting Simon Whistler here, is that they have never been used this way while in war time. This would be essentially funding one side’s war machine and could come back to bite western countries if they opt to overthrow a bad actor in the future.
For example, what if Bashar Al-Assad decides on the heavy use of chlorine gas on the majority Sunni in his country. The West opts to overthrow. The West are then the aggressors. Does Euroclear then freeze US assets and give them to Assad according to the precedent set by Russia v Ukraine?
The judiciary likes to follow precedent and consistency, it fairs less well when there is nuance and subject to interpretation. From a geopolitical standpoint, do we really want the judiciary determining who the good guys and the bad guys are?