U.S. lets scofflaw gun dealers continue to arm criminals:
"Multiple offenders make up only about 1% of the nation's 104,000 licensed gun dealers. But federal statistics indicate they are the source of more than half the guns used in crimes. The problem of scofflaw dealers was underscored by a report Tuesday by the Americans for Gun Safety Foundation, which favors tougher enforcement of existing laws." (empasis mine)
In most cases, the immediate "solution" is to pass more laws. This article shows some reasons why current laws are seldom enforced.