Final answer:
The Fair Housing Act is the law that makes it illegal for real estate lenders to redline a neighborhood.
Step-by-step explanation:
The law that makes it illegal for real estate lenders to redline a neighborhood is the Fair Housing Act. Passed in 1968, this law outlawed redlining and other forms of housing discrimination. Redlining is the process of designating neighborhoods as unacceptable credit risks based on their racial demographics. The Fair Housing Act sought to eliminate this discriminatory practice and promote fair and equal access to housing for all individuals.