There are many Nigerians that produce products in Nigeria.  These products can be bought and used in Nigeria.  This will keep the money in Nigeria.  The profits made from the Nigerian products can be used to invest in more factories.  This will create jobs, increase internal government revenue, increase production, reduce importation, and promote exports.  With better economic production, then the crime rate will be reduced.  When you buy imported foreign goods, then money is leaving the country.  There are many products that are produced in Nigeria.  Everybody can buy these products.