Arguing for the continued confidentiality -- and subsequent destruction -- of the records in front of the U.S. Court of Appeals for the Ninth Circuit are representatives of the Major League Baseball Players Association.
"Our program, which was designed to be confidential, if it turns out not to be, that's something that causes concern," said Donald Fehr, MLBPA executive director, on the eve of the proceedings.
Setting up Wednesday's case were three prior judicial victories by the union, with three federal district judges ruling that the government violated the Fourth Amendment in seizing the list and all the corresponding urine samples rather than only those of 10 players involved in the BALCO scandal.
The appellate case comes two days after Alex Rodriguez confessed to being one of the 104 players, confirming details that were reported in a weekend SI.com story that he had used "banned substances" while a member of the Texas Rangers from 2001 through 2003.
If prosecutors get the green light to use the list and other players are subpoenaed to appear before grand juries and trial courts, other names might be made public.
Meanwhile, according to ESPN, at least eight of the 104 players on "the list" tested positive for substances that were not on baseball's banned list at the time.
ESPN, citing a highly placed Major League Baseball source, reported that the 2003 test results of these eight or more players "were consistent with then-available over the counter supplements not banned by baseball until 2005."
Fehr declined comment on the report Wednesday, but told ESPN on Tuesday that, "what we knew is that their names were on a list and, as I said, it could be because the government thought they tested positive, it could be that they wanted information for some other reason, it could be because there was a mistake. All we knew is that they were on a list."
Tom Singer is reporter for MLB.com. Reporter Doug Miller contributed to this story. This story was not subject to the approval of Major League Baseball or its clubs.