One example of where common law was overridden by the passage of a federal statute is the ruling in the Obergefell vs Hodges case where they legalized same-sex marriage on a federal level, which trumped some states in which same-sex marriage was illegal.
Common law is made by judges in a court, using precedent decisions made in previous similar cases to decide how they will judge a case before them. If no past cases with similar circumstances exist, a new decision is made, which would then become a precedent for a future similar case. If no statute law, law made by Parliament applies to cover a particular situation, common law will apply; however, statute law always overrides common law.