how were slavery, equal protection under the law, and voting right for black men addressing following the civil war

After the American Civil War (1861-65), the US Congress passed a series of Acts such as ...

the creation of the Freedmen's Bureau which was a War Department agency for assisting freed slaves in obtaining jobs, food, health care, fair treatment, and education; the Civil Rights Act of 1866 which affirmed that all citizens were equally protected by the law; several Reconstruction Acts which gave former male slaves the right to vote and hold public office;

The Congress also passed the Fourteenth and Fifteenth Amendments to the Constituion which made African-Americans citizens, guaranteed their right to vote and protected American citizens from discriminatory state laws.

The 14th Amendment to the US Constitution, ratified in 1868, granted citizenship to all persons born or naturalized in the United States, including former slaves and guaranteed all citizens equal protection of the laws.

One of the three amendments passed during the Reconstruction era abolished slavery and established civil and legal rights for black Americans.

But many Northerners got very angry when the newly elected southern state legislatures, dominated by former Confederate leaders, enacted black codes, which were repressive laws that that strictly regulated the behaviour of black citizens and effectively kept them dependent on white planters.