On the eve of learning whether he can give his 11 guns to his son, the long arm of the law came down on Drew Peterson because one of his weapons was too short.

Peterson surrendered to state police Wednesday after he was notified of a warrant for his arrest on a charge of felony unlawful use of a weapon. By midafternoon, he was on his way back home after posting 10 percent of a $75,000 bond.

The charge, which carries a potential penalty of up to 5 years in prison, alleges Peterson "knowingly possessed a rifle, namely a Colt model Sporter Lightweight, 223 Remington rifle . . . with a barrel less than 16 inches in length," in violation of state law, the Will County state's attorney's office said.

The former Bolingbrook police sergeant has been engaged in a court battle to regain possession of his guns from state police, who seized them Nov. 1as part of a search warrant at his home.

Peterson, 54, has been named a suspect in the Oct. 28 disappearance of his fourth wife, Stacy, who was 23 at the time. Authorities are also conducting a murder investigation into the 2004 drowning of his previous wife, Kathleen Savio. Peterson has not been charged in those cases and maintains he has done nothing wrong.

His attorney, Joel Brodsky, said Wednesday's arrest was an attempt to rattle his client.

"This came as a total surprise this morning," he said. "We were thinking if he was ever arrested that it would not be a bondable offense.

"They may believe it's a tactic to shake him up, but it's certainly not going to work," he said. "Drew was joking with police officers when he was taken into custody."

Peterson shouted, "I love you" to reporters gathered outside the house as he left to turn himself in.

After his release, though, he appeared subdued and declined to comment on the advice of Brodsky. When asked if he felt he was being harassed, Peterson answered, "You think?"

Peterson retired from the Bolingbrook department in November, but Brodsky said he was still an officer when the gun was seized.

"The state police had this weapon in their possession before he retired, so there is no basis for this charge," he said. "He was a SWAT team member and he was allowed to have two duty weapons. This was a registered duty weapon with the Bolingbrook Police Department, and he carried it for 10 years.

"The timing is very suspicious that they would wait until the day before we were supposed to get the court order that the guns be returned to his son," he said. "I think the Illinois State Police are fixated on these guns. . . . I don't understand it. It's not logical."

Brodsky said it must mean the investigations concerning the two wives are going nowhere, a theory the state police disputed.

"We feel the case is progressing well," Sgt. Thomas Burek said in front of the courthouse. "An arrest will be made."

Authorities confirmed that Wednesday's arrest was made in light of the expected ruling on whether Peterson can transfer ownership of his guns to his son Steven, an Oak Brook police officer. At a hearing last week, Judge Richard Schoenstedt appeared to signal that he would grant Peterson's request.

"The weapon was illegal, and it was privately owned," said Charles Pelkie, spokesman for the state's attorney's office. "Up to this point, it's been in the possession of the Illinois State Police so it wasn't really an issue. But we can't allow an illegal weapon to go back out on the street. At this point, it was appropriate to file the charge."

Pelkie said the rifle barrel was slightly more than 11 inches long—almost five inches shorter than required by law. He said that even with a removable flash suppressor attached to the end—which legally cannot be considered part of the barrel—the gun was still too short.

While state law provides an exemption for law enforcement to carry a shorter weapon, Pelkie said that does not apply to Peterson but declined to say why.

Bolingbrook police spokesman Lt. Ken Teppel said the weapon was not issued by the department, and any personal weapons owned by Peterson must be lawful. Teppel said, "If it's a personal weapon, he is still bound by state law, federal law."

The arrest—while tangential to the search for Stacy Peterson—initially brought hope and excitement to the missing woman's relatives, though it was quickly tempered when they learned more about the nature of the charge.

"We were, of course, very hopeful when we heard that he was going to be arrested," said Pam Bosco, spokeswoman for the family. "But as we found out more, I can't say we were disappointed, but . . . our hearts leaped from our chests when we first heard there was going to be an arrest."

She said Peterson should be prosecuted if he is guilty of having an illegal weapon.

"We don't want to see anything that's not being done according to the law, especially if these guns are going to be returned to his family members," Bosco said.

Tribune reporter Emma Fitzsimmons contributed to this report.

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