A320 can be stalled in alternate and direct control laws and alternate law is what one gets when: two or all ADRs (air data reference) fail, all three ADRs disagree or one fails and two others disagree (the list is not exhaustive).
Sadly, the XL crew has demonstrated that A320 can be stalled in normal law too, provided both AoA inputs are valid, in agreement and way below actual AoA.