Theodulo Nava Reyes v. United States

"(a) In order further to give effect to the obligations of the United States pursuant to the Hague convention of 1912, proclaimed as a treaty on March 3, 1915 (38 Stat. 1912), and the limitation convention of 1931, proclaimed as a treaty on July 10, 1933 (48 Stat. 1571), and in order to facilitate more effective control of the international traffic in narcotic drugs, and to prevent the spread of drug addiction, no citizen of the United States who is addicted to or uses narcotic durgs, as defined in section 4731 of the Internal Revenue Code of 1954, as amended (except a person using such narcotic drugs as a result of sickness or accident or injury and to whom such narcotic drug is being furnished, prescribed, or administered in good faith by a duly licensed physician in attendance upon such person, in the course of his professional practice) or who has been convicted of a violation of any of the narcotice or marihuana laws of the United States, or of any State thereof, the penalty for which is imprisonment for more than one year, shall depart from or enter into or attempt to depart from or enter into the United States, unless such person registers, under such rules and regulations as may be prescribed by the Secretary of the Treasury with a customs official, agent, or employee at a point of entry or a border customs station. Unless otherwise prohibited by law or Federal regulation such customs official, agent, or employee shall issue a certificate to any such person departing from the United States; and such person shall, upon returning to the United States, surrender such certificate to the customs official, agent, or employee present at the port of entry or border customs station.