FOX ISLAND, Washington (Reuters) - On a recent afternoon Kent Holder drove his Ford pickup truck, emblazoned with "Citizens' Patrol" magnetic decals, through this leafy enclave west of Tacoma, Washington, recalling when he learned that George Zimmerman had shot and killed an unarmed teenager - and was a neighborhood watch volunteer.

"I thought, âÃ‚â‚¬Ã‚ËœBoy, did he ever screw up,'" said Holder, 74, a retired fireman and five-year neighborhood patrol veteran.

In Holder's view, Zimmerman violated two basic tenets of the watch program: Never confront a person you perceive to be suspicious, and never carry a weapon while on duty.

Last weekend, a Florida jury acquitted Zimmerman, 29, of second-degree murder and manslaughter charges in the 2012 shooting death of Trayvon Martin, who was unarmed, in Sanford, Florida. The case has focused fresh attention on the civilian patrols by law enforcement and trainers.

Zimmerman, 29, who is white and Hispanic, spotted Martin, who was black, as the teenager walked to the home of his father's fiancÃ©e from a convenience store. Zimmerman thought Martin looked suspicious and called the police. The two had a confrontation and Martin ended up dead.

The National Sheriffs' Association's neighborhood watch program was established in 1972 to combat a spike in suburban and rural burglaries.

It was designed to empower civilians to act as "the eyes and ears of law enforcement" without taking matters into their own hands, said John Thompson, who directs the initiative. The association's 37-page manual states that patrol members should be told that "they shall not carry weapons."

While the group is seen as an authority, fewer than a third of the estimated 90,000 neighborhood watch groups in existence nationwide have registered with it, said Thompson. Zimmerman's watch group was not among those registered, he said.

"I could show you 50 groups with 50 different sets of rules," Thompson said.

During the trial, Wendy Dorival, a civilian with the Sanford, Florida, police department, testified that she trained Zimmerman on neighborhood watch protocol, advising him to avoid initiating confrontations. It was not clear whether she counseled him on whether to carry a gun.

Barring guns from civilian patrols is a legal gray area since most U.S. citizens have the legal right to bear arms, said Kenneth Novak, a criminologist at the University of Missouri-Kansas City, who has studied watch programs.

Local watch groups, as private entities, are on relatively firm legal ground in setting no-weapons policies for their members, Novak said, but law enforcement agencies mandating such rules could run the risk of exceeding their authority.

"People participating in neighborhood watch enjoy all the legal protections under the Constitution, as well as state and federal law," said Novak. "That can include carrying a weapon."

Jeffrey Dehan, a sergeant who advises neighborhood watch groups as part of his duties with the Thurston County Sheriff's Office in Washington state, says it is not their role to offer guidance on whether members should carry a weapon.

"We don't advocate 'should or shouldn't,'" he said.

Carmen Caldwell, the executive director of Citizens' Crime Watch of Miami-Dade, in Florida, said that in the wake of the Zimmerman case, some trainers and others were considering new safeguards, which could include background checks on prospective members and teaching about racial profiling.

Holder, the ex-fireman from Washington, said fallout from the Trayvon Martin shooting has been minimal.

"There was concern that we would've had something negative from it," he said. "But nobody has ever said, 'You guys shouldn't be out here.' They love us. They love having us."

(Editing by Prudence Crowther)