What was the significance of the first battle of bull run

It marked the first Confederate victory.

The union defeat made it clear that the north would need a large, well trained army to defeat the south.

Explanation: Hope this helps :)

the doctrine of nullification recommended that states living inside the union have the one-sided, inalienable ideal to void any law made by the national government that could be esteemed illegal.

the united states was shaped based on a general agreement among its individual states. hence, it is inferred that under the hypothesis of invalidation, since the states are the establishment of the union, they have the ability to referee and disprove unlawful laws.