Calvin did not believe all Old Covenant laws had been set aside by the New Covenant Jesus inaugurated. He didn't buy into the plain sense of Hebrews: “God has made the first covenant obsolete” (Hebrews 8:13). He maneuvered around Paul’s conclusion: “the Law became a tutor to lead us to Christ and now that faith has come we are no longer under a tutor” (Galatians 3:24-25; cf. Rom 10:4). Therefore, laws from the Torah guided his actions.
Calvin justified capital punishment of heretics with Leviticus 24:16. “The one who blasphemes the name of the Lord should be put to death; all the congregation must stone him. Any foreigner or native who blasphemes the Name should be put to death.”
Jesus’ teaching to “love your enemies” didn’t stop Calvin from killing them. Paul’s instructions for dealing with people who theologically disagree with you were ignored: “A servant of the Lord must not quarrel but must be kind to everyone, be able to teach, and be patient with difficult people. Gently instruct those who oppose the truth. Perhaps God will change those people’s hearts, and they will learn the truth” (2 Timothy 2:24-25). Calvin authorized beheadings, death by fire, and torture rather than exercise patience and kindness with competing theologians. His enforcement of biblical doctrines looked more like ISIS than Jesus.