What effect did the Enforcment Acts have in Southern states?
The first of the three acts was passed in March of 1870. The Enforcement Acts were:
criminal codes that protected blacks' right to vote, hold office, serve on juries, and receive equal protection of laws. If the states failed to act, the laws allowed the federal government to intervene.
One effect that this act had is that many Ku Klux Klan members were brought in for trail but very few were convicted. Many whites would not testify because they did not agree with the act and many blacks would not testify because they were afraid of standing up against the whites.
In several counties in South Carolina martial law was declared and many Klansman were sent to jail, ran off, or were hit with warnings and fines. By 1872, the Klan was broken but this only lasted for a few years.
I assume that you are talking about the Enforcement Acts that were passed by Congress in 1870 and 1871. These acts were meant to protect the rights of the newly freed slaves and to suppress the KKK. While these acts did not have a long lasting effect, they did have a short term impact on the Southern states.
Most significantly, the acts ensured that black rights would be respected by Southern governments. The acts also ended up breaking the KKK's power in the South.
Of course, these effects only lasted a few years as Reconstruction ended in 1877.