veto against, veto on, veto over

A legal or official body with the authority to reject a plan or prohibit an action has a power of veto. The plural is vetoes.

The noun veto is followed by against, on or over, or no preposition.

• Some Security Council members will cast a veto against a UN resolution sanctioning military intervention.
• The federal government has a right of veto on all aspects of constitutional amendments.
• Without a quorum, the members were unable to override the veto.

The verb veto does not require a preposition.

• The board of directors vetoed the plan to buy out the competition.

Informally, veto is used as a synonym for reject or forbid.

• Every time Simon makes a proposal, Danielle vetoes (or rejects) it.