"We have every confidence [the judge] would consider the issues before him. He did that. We're looking forward to prosecuting this case and moving forward. That's really about all I can say," said Charles Pelkie, Will Co. state's attorney spokesman.
A grand jury indicted Peterson on two felonies related to a semiautomatic rifle seized by authorities investigating the disappearance of his wife, Stacy. Authorities contend Peterson possessed an assault rifle with a barrel shorter than allowed by law.
Peterson has been named a suspect in Stacy's disappearance but hasn't been charged.
Defense attorney Joel Brodsky argues his client is immune from prosecution for the gun charges because he was still a police officer when authorities seized the weapon.
"Under state law, this is Drew's secondary duty weapon. He was approved to use it, and we have documents to show that and that under state law, he was exempt from any barrel length restrictions. Then thirdly, we're going to prove the last leg of the exemption. We have three very solid arguments for trial," said Joel Brodsky, Peterson's attorney.
A pre-trial date has been set for August 28.
The Associated Press contributed to this report. All rights reserved.