What condition leads to switching from normal law to alternate law?

The transition from normal law to alternate law in the A320's flight control laws is primarily influenced by the failure of the aircraft's electronic and electrical systems. When there is a malfunction or failure in any of the key electrical components that support the flight control system and provide data to the flight computers, the aircraft is unable to maintain the normal law with its full range of protections (such as stall protection and load factor limiting).

In simple terms, if electrical systems that process essential flight data experience a malfunction or failure, it compromises the fundamental capabilities of the aircraft to operate within normal law parameters. As a result, the flight control system defaults to alternate law to ensure continued flight capability, albeit with reduced protections, such as the absence of some automatic protections and limits.

Additional factors influencing the transition to alternate law might include hydraulic failures or single ADR failures, but the critical aspect in this case is the electrical systems malfunction, which directly impacts the overall operation and safety features of the aircraft.