Is it Pennsylvania law, that an employer must pay an employee unused paid vacation time at the time of layoff?

Company handbook states you must give up your unused vacation at the end of the year with my husbands title excluded so this does not apply to him.

He is being layed off at the end of October and they stated they will not be paying him his 24 days of unused vacation. Can they do this when he has an email stating the handbook does not apply to him and his vacation carries over?