JEFFERSON CITY, Mo. -- Opponents of Missouri's new concealed-gun law are attempting to shoot it down before it takes effect. They plan to file a lawsuit Wednesday claiming it violates various parts of the Missouri Constitution.

The lawsuit, a copy of which was obtained by The Associated Press, seeks both an injunction blocking the law from taking effect Saturday and a permanent declaration striking it down. It claims a provision of the Missouri Constitution dating to 1875 prohibits the wearing of concealed firearms and it alleges the new law unconstitutionally imposes a requirement on counties without providing funding to cover the increased costs.

The lawsuit also claims the legislature unconstitutionally usurped the power of the people by passing a law similar to one that voters narrowly rejected in an April 1999 referendum.

State Sen. Harold Caskey, D-Butler, a lawyer and longtime concealed guns supporter who co-sponsored the bill, said the allegations "are of no merit" and the lawsuit "is a desperate attempt to prolong the issue."

Lead House sponsor Rep. Larry Crawford, R-Centertown, said the plaintiffs merely "are whining that their way wasn't the way of the people who were elected."

Both sponsors had received and reviewed copies of the lawsuit Tuesday.

A spokesman said Attorney General Jay Nixon, who will defend the law, had no comment.

The Legislature initially passed the concealed-guns bill in May, but Gov. Bob Holden vetoed it. Then last month, lawmakers overrode Holden's veto by a two-thirds majority vote -- enacting the measure without need of the governor's signature and without putting the issue to another statewide vote.

Holden has not seen the lawsuit, but "the governor believes there are many flaws in the law that could invite a lawsuit," spokeswoman Mary Still said.

The law allows Missourians age 23 and older who pay up to $100 and pass a criminal background check and an eight-hour training course to receive permits from their county sheriffs to carry concealed guns. It also allows anyone age 21 or older to conceal a gun in a vehicle without needing a permit.

St. Louis attorney Burton Newman said in a letter to Nixon's office that the lawsuit will be filed Wednesday in St. Louis Circuit Court. Newman declined to comment Tuesday but said a news release would be issued Wednesday about the lawsuit.

Other arguments raised by the lawsuit include an assertion that the law is an improper use of the Legislature's police power and is so vaguely worded that it is unconstitutional. The lawsuit cites 23 examples of allegedly vague words and phrases.

The lead plaintiff is Kansas City councilman and mayor pro tem Alvin Brooks, who said in an interview that numerous attorneys who reviewed the law have described it as "the worst piece of legislation they've seen."

"It's got too many loopholes in it," said Brooks, who also is leading an effort to keep concealed guns out of Kansas City government buildings. "I'm committed to nonviolence, I'm committed to peace and love and understanding that transcends race and ethnicity and religion and urban and rural and suburban."

The 10 plaintiffs include three Democratic state senators who voted against the bill -- Sens. Joan Bray, Rita Days and Maida Coleman, all of St. Louis.

Bray said Tuesday that she had not yet seen the lawsuit and so could not speak about its details. But she said she lent her support to the lawsuit because St. Louis voters had opposed the 1999 ballot measure.

"My constituents voted overwhelmingly when they had the opportunity to speak about the issue, and they feel betrayed by the Legislature. I'm representing my constituents," Bray said.

Other plaintiffs include Hazelwood Police Chief Carl Wolf, Bishop Willie James Ellis of the New Northside Baptist Church in St. Louis, Pastor B.T Rice of the New Horizon Christian Church in St. Louis, St. Louis alderman Lyda Krewson, Jackson County legislator Scott Burnett and a nonprofit group called the Institute for Peace and Justice.