Is there an Usuli legal maxim that states: "If the 'illah (effective cause) becomes void, the hukm (ruling) becomes void"? And can this be applied to the 'illah of Isbal (letting one's garment hang below the ankles) being pride and boasting, such that if this 'illah is absent in Jordanian society, is it permissible to lengthen one's garment to slightly below the ankles?

The wearer of a garment that extends below the ankles commits a sin, whether this is due to arrogance and pride or not. The sin and the warning increase if it is due to arrogance or pride. It is not correct to restrict the hadith "Whatever is below the ankles of the izar is in the Fire" with the hadith "Whoever drags his garment out of pride." The prohibition of both matters is mentioned in one hadith: "The izar of the believer is to the middle of his shins; there is no blame on him for what is between that and the ankles. Whatever is below the ankles is in the Fire," saying three times: "Allah will not look at one who drags his garment out of boastfulness." Therefore, the cause is not arrogance alone; rather, lengthening the garment with arrogance is a greater sin.