Lawyers for Moore, whose "Fahrenheit 9/11" has become a box office success, and James Nichols, the brother of Terry Nichols, argued Wednesday in federal court over a lawsuit seeking millions of dollars, the Detroit Free Press reported Thursday.
Judge Paul Borman told both sides he would have a decision in about a week about whether the case would proceed to trial.
James Nichols filed a lawsuit last October claiming he was tricked into appearing on camera for Moore's 2002 documentary, "Bowling for Columbine." Nichols alleges Moore libeled him by linking him to the Oklahoma City bombing for which his brother was convicted.
Moore is accused of nine counts, including libel and defamation of character.
Nichols' attorney, Stefani Godsey, asked for a jury trial and damages up to $20 million on each count.
Moore's attorney argued the case should be thrown out because the one-year statute of limitations for libel claims had run out.