Stop Gun Trafficking and Strengthen Law Enforcement Act of 2011 - Amends the federal criminal code to prohibit any person from: (1) receiving, or transferring or otherwise disposing of to one or more individuals, two or more firearms that have been shipped or transported in interstate or foreign commerce, knowing or having reasonable cause to believe that such conduct will result in the disposing of one or more such firearms to an individual whose possession or receipt of the firearm would be unlawful or who intends to or will use, carry, possess, or dispose of the firearm unlawfully; (2) knowingly directing, promoting, or facilitating such conduct; or (3) conspiring to commit such conduct.