The doctrine of estoppel is based upon the grounds of public policy, fair dealing, good faith, and justice, and its purpose is to forbid one to speak against his own act, representations, or commitments to the injury of one to whom they were directed and who reasonably relied thereon upon. Said doctrine springs from equitable principles and the equities of the case.
The Common Law is a body of law derived from judicial decisions known as case laws, rather than from statutes. The Common Law derived its authority from the universal consent and practice of the people from time immemorial. This system of jurisprudence initially originated in England.