A node is required to validate if an event is valid before adding it to the event chain. Events that are invalid may be rejected.
Live Contracts draft 01 does not yet include specifications for rejects. Events that don't validate are silently dropped. This may give problems in Live Contracts implementations that support distributed contracts.
Each event SHOULD be validated before adding it to the event chain. This means verifying that
The signature of the event is valid
The hash of the event matches
The event is less than 15 minutes old and has an receipt
The event receipt can be verified