Thanks for clarifying the point re: federal government department employees. What are avenues for US based employees to seek arbitration in cases like the OP,

Thanks for clarifying the point re: federal government department employees. What are avenues for US based employees to seek arbitration in cases like the OP, where leave entitlements and agreements are abused? What if someone had to take time off to, say, care for a sick family member and they had 'n' days leave owing to them and their employer would not let them take it? Can there be some non legal industrial mediation, or must they take it to court?