Jamieson, Fausset and Brown on 1 Corinthians 15:56

56. If there were no sin, there would be no death. Man's transgression of the law gives death its lawful power.

strength of sin is the law--Without the law sin is not perceived or imputed (Ro 3:20; 4:15; 5:13). The law makes sin the more grievous by making God's will the clearer (Ro 7:8-10). Christ's people are no longer "under the law" (Ro 6:14).