Date: 4 Menachem Av 5571
From: Rabbi Moshe Sofer
To: Unknown recipient
A student who doubted the validity of his heter iska and wished to return ribis as an act of teshuvah asked whether he must repay at the inflated government-mandated rate following currency devaluation. The Chasam Sofer rules that the student need only return the same nominal number of banknotes he originally received, because dina d'malchusa dina applies only within the scope of governmental intent, and the government's debt-repayment decree was never meant to govern the uncommon Torah-driven act of returning ribis.
Source: Shu"t Chasam Sofer CM §62