What happens to the government's authority when a person dies?
When a person dies, the government's authority over that person ceases completely. The law has dominion only as long as a person lives. At death, the government loses all control; it cannot tax the deceased or do anything to them. Death severs that legal jurisdiction.
Les explains that Paul is not merely discussing the Mosaic law in Romans 7:1, but law as it governs society. Just as believers live under the United States government and the Constitution, that constitutional law controls them only until they die. The moment a person dies, the American government loses all control. It cannot tax a dead person or do anything to them. Paul is driving at the truth that the only way some things can be severed is by death.
Know ye not, brethren, (for I speak to them that know the law,) how that the law hath dominion over a man as long as he liveth?