The Supreme Court dismissed the case due to the lack of standing of the plaintiff. The Court ruled 7-2 that the plaintiff lacked standing to bring the lawsuit in federal court because he was not a US Citizen and so his individual rights were not protected by the Constitution. While the plaintiff was born in the United States, his parents were not considered citizens.
The decision was described in Doris Kearns’ book, Team of Rivals.
Two days later, on March 6 , the historic decision was read by the seventy-nine-year-old Taney …. The 7-2 decision was breathtaking in its scope and consequences. The Court ruled that blacks “are not included, and were not intended to be included, under the word ‘citizens’ in the Constitution.” Therefore [Dred] Scott had no standing in federal court. This should have decided the case, but Taney went further. Neither the Declaration of Independence nor the Constitution had been intended to apply to blacks, he said. Blacks were “so inferior that they had no rights which the white man was bound to respect.” …
By the 1850’s, one historian reports:
Taney had become an uncompromising supporter of the south and slavery and an implacable foe of racial equality, the republican party, and the antislavery movement.
This case is the foundation of modern birtherism based on Barack Obama’s African father.