Safe harbor is a regulation or statute which states that particular conduct does not count as a violation of a specific rule. For example, an employment contract may state that staff members must not accept gifts from customers, but a clause that notes that gifts under a value of $25 are acceptable would be considered a safe harbor.
Unsafe harbor, by contract, defines conduct that would be in violation of the rule. Using the same example above, it may say that gifts worth $25.01 and above are in violation of the no-gift policy. These types of rules and clauses are essential to review when determining whether an employee has engaged in gross misconduct.