How can a presidential veto be overridden?

A presidential veto can be overridden by a two-thirds vote in both houses of Congress, which is a constitutional requirement outlined in Article I, Section 7 of the U.S. Constitution. This process ensures that a substantial consensus among lawmakers is necessary to counteract a president's refusal to approve legislation.

The rationale behind requiring a two-thirds majority is to ensure that the legislative branch has a significant level of agreement before it can proceed with a law that the president opposes, reflecting a balance of power between the legislative and executive branches. This high threshold prevents legislative whims from overriding presidential objections and encourages collaboration and negotiation between branches of government.

The other options do not provide a valid mechanism for overriding a presidential veto. A simple majority would be insufficient, as it does not meet the constitutional requirement. Presidential decree does not apply, as the president cannot unilaterally change legislative decisions. Finally, a state referendum would not factor into federal law processes, as state-level voting does not have jurisdiction over congressional actions or decisions made at the federal level.