What is the ruling of Islamic law on not reporting a person who is defrauding asylum law by withdrawing monthly refugee allowances after returning to his home country, knowing that he is thereby taking the right of others and violating the law?

If a person takes the right of another and violates asylum law through deception, this is a reprehensible act that must be denounced and changed. If the questioner is able to do so and does not fear harm to himself, he is obliged to do it. Otherwise, everyone who was able to change it and did not do so would be sinful.