I live in the 'West Caribbean'. The Muslims here are assimilating to the local people's lifestyle including dress. We see men wearing short pants above the knees showing their thighs. Please issue a Fatwa with Sharia evidence refuting this practice, so that I may present it to the Muslims here. Thank you very much, may Allah bless you with all that is good.

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

The majority of the scholars are agreed that the Awrah of the man is what is between his navel and his knee. They do not consider the navel itself and the knee as Awrah, except the Hanafi school that considers the knee as a part of Awrah.
So the Muslim should not wear shorts that do not cover his thigh as failing to do so means publicly uncovering his Awrah.
Ahmad reported from Jurhud that the Prophet (Sallallahu Alaihi wa Sallam) saw a man with his thigh uncovered and he said to him: "Cover your thigh as the thigh is Awrah" .
Abu Dawood and al-Daruqutny reported that the Prophet (Sallallahu Alaihi wa Sallam) said to Ali : "Do not uncover your thigh and do not look at the thigh of a dead person or a live one" .
These two Hadith are enough evidence that the thigh is part of the Awrah. So the person should not uncover it or look at the thigh of another person.
There is yet another sin; wearing these shorts is imitating what the non-believers wear and the Prophet (Sallallahu Alaihi wa Sallam) forbade us to imitate non-believers.
So, Muslims should cover their Awrah and should not imitate non-believes. They should abide by the rules of their religion.
Allah knows best.