The Black Codes were laws passed by Southern states in 1865 and 1866. It's intent was to restrict African American's freedom and force them to work in a labor economy based on low wages or debt, very similar to slavery. The purpose of these was to maintain white supremacy in some people's eyes.
Dillingham Commission was created due to the extensive numbers of immigrants coming into the United States. This was a record that kept track of the immigrants who entered so the government could place restrictions and laws against immigration because it was becoming uncontrollable.
The Immigrant Restriction League was designed to try and limit immigration in the United States. They doubted the ability of the government to control the amount of immigrants, and tried to act on their own. The members thought of immigrants as the cause of social and economical problems and felt it necessary for there to be restrictions.