All of the people in our company are employed "at will", but some will be laid off for a definite period and the plan is to employ them again after several months. Can any criteria that the company chooses be used to select the people who will be laid off? It was suggested by one of our managers that one of the criteria that the company should use for selecting the people who will be laid off is seniority. Other managers want to use job performance as the criteria for selection. What criteria may be legally "off limits" to the employer?

You can not layoff by religion, sex, age and other protected classes.

You can layoff all the red haired people ( as long as it is not a nationality things) you can lay off every other person standing in a line if you want.

But seniority is the more normal way of doing it, but production is also used at times