Essentially the nonsense they were waffling about boils down to one simple fact: confiscation.
When you confiscate something it's taken from you grasp and you're not expected to get it back, right? Well, Higurama's domain works like that.
Imagine it as a school where teachers take dangerous objects immediately. Except the 'student' - in this case being Sukuna - was holding more than one dangerous object (think of it as a teacher expecting to take a phone but finding out you have a knife as well).
The aim of Higurama's technique was to 'condemn' Sukuna to death penalty (blame him for killing all the people in Shibuya), which would automatically take away his technique. However, they didn't notice Sukuna was HOLDING a weapon. So, Higurama's domain (Judgeman) counted it as a danger, confiscated it and took the WEAPON Sukuna physically HELD instead of his technique... like Itadori and Higurama expected.
So, now they're in a tight spot.
Can someone explain me the conclusion about confiscation? In a simple language