A neo-Nazi group has joined the state's "Adopt-A-Highway" volunteer litter pickup program, taking advantage of a free speech court fight won four years ago by the Ku Klux Klan.

The Springfield unit of the National Socialist Movement has committed to cleaning up trash along a half-mile section of Highway 160 near the Springfield city limits.

Two signs noting the group's membership in the Adopt-A-Highway program went up in October but drew attention only recently when the group picked up litter as part of a gathering in Springfield.

The state says it had no way to reject the group's application. A 2005 U.S. Supreme Court ruling arising from a similar effort by the Ku Klux Klan says membership in the Adopt-A-Highway program can't be denied because of a group's political beliefs. At the time, the state could reject applications for the program from groups that denied membership based on race or had a history of violence.

"It's a First Amendment thing, and we can't discriminate as long as they pick up the trash," said Bob Edwards, a spokesman for the transportation department's office in Springfield.

The state can deny an organization's application only if it has members who have been convicted of violent criminal activity within the past 10 years.

The NSM Springfield unit decided to take part in the highway project because it wants to clean up the community, said Ariana Glass, a 16-year-old member of the youth division of the group.

"We wanted to prove that we're not out here just to have fun, we want to make the community look good," Glass said.

The group heard both honks of support and jeers when about 30 members and supporters picked up trash Saturday. Greene County sheriff's deputies ticketed one man who group members said became threatening but there were no other incidents, Glass said.

Members of the highway cleanup program are required to clean up trash at least four times a year. Edwards said about 600 groups pick up trash in the 12 counties surrounding Springfield.

Edwards said his department had received only one phone call asking why the National Socialist group was allowed to adopt the highway. Louise Whall, spokeswoman for the city of Springfield, was not aware of the group's action until contacted by the AP, but said the city had no jurisdiction because it's a state program.

Most other states have programs similar to Missouri's. Ten states — Alabama, Arkansas, Hawaii, Illinois, Kansas, Maryland, Oklahoma, Pennsylvania, Texas and Vermont — had joined in filing a brief backing Missouri's side in the court fight.