There are no laws whatsoever dictating when, in what order, or even whether, a laid off employee must be paid back.
If there is a union or other legally binding contract that does have such an order, then the contract/CBA would apply. If there is such a contract or CBA, we have not read it; therefore we cannot tell what, if any, order is mandated.
If there is no union or other contract specifying how a laid off employee is called back, then it's entirely up to the employer whether or not to call back laid off employees at all, and if so, under what terms or in which order.