Why lawyers need historians in maritime disputes

Why do historians sometimes get called upon by lawyers?

Usually for international or maritime-law questions involving precedent and imprecise wording. The comparison with domestic law is limited to personal experience and allows for exceptions.

No domestic-law cases come to mind from personal consulting experience, though such cases may exist. International and maritime law are the usual fields for these requests, including questions where the two overlap. Precedent can make earlier legal wording matter. If that wording lacks precision, lawyers have a reason to call on historical expertise.