Question

Which two arguments did the Supreme Court use to uphold the constitutionality of Korematsu’s internment?

Due to the war, there was not enough time to hold trials or hearings before sending people to internment camps.

The military had a legitimate need to protect against espionage and sabotage.

Korematsu had been proven a Japanese spy and a threat to national security.

Answer 1

The first and second.
The Court accepted the government's claim of military necessity (a legitimate need to guard against espionage/sabotage) and said wartime urgency made individualized trials/hearings impractical. It did not find Korematsu to be a proven spy.