Roosa from returning to the Air Force when he left NASA, leading him to go into business instead. Although Apollo 16's Charles Duke had taken covers to the lunar surface in April 1972, changes to the PPK procedures instituted by NASA meant that none were taken on Apollo 17 that December. Today, astronauts are forbidden by federal regulation from taking philatelic items into space as mementos. The remaining covers in the Apollo 15 astronauts' control (298 from the group of 400 and 61 more from Worden) were held by NASA during the investigation; Worden said he surrendered them at Kraft's request on the understanding they would be returned once the investigation was over, but the covers were transferred to the National Archives in August 1973. There was a Justice Department investigation into the covers. Its Criminal Division decided in 1974 that no prosecution was warranted, but the Civil Division the following year assumed the covers would be retained by the government. Kraft wrote, "it was questionable that any law had been broken and [the Justice Department] realized that dragging astronauts into court would not be a popular pastime." In December 1978, the Justice Department issued a report indicating that while the government might have some claim to the Herrick covers (due to the appearance of having been made for profit), it probably did not have any claim to the 298 remaining covers, which the astronauts had said were intended as gifts. The department sent a secret memo to NASA that same year, effectively stating that the government took the covers without "any legal proceedings against the astronauts," and in the process "may have violated their constitutional rights," according to a press source in the Justice Department. In 1979, the department informed NASA that it had concluded that the government would likely lose if the astronauts sued for the covers. There was opposition among senators to the covers being returned, and in February 1980 Howard Cannon of Nevada introduced a joint resolution that the government should keep the covers because of their commercialization and advise the Attorney General to "defend any civic action brought" regarding them. It passed the Senate but died in the House of Representatives. In February 1983, Worden sued, alleging NASA violated the Constitution by seizing the covers without a hearing. At this time, the Justice Department reminded NASA of its 1978 secret memo. The government concluded NASA