(JEFFERSON CITY, Mo., AP) — As state attorney general, Chris Koster is sometimes referred to as Missouri’s top prosecutor. But as the nationally publicized case of an alleged teenage sexual assault has shown, Missouri’s attorney general has relatively limited powers to prosecute people.

In fact, the attorney general typically must be invited to do so.

The powers of Missouri’s attorney general became an issue after The Kansas City Star reported last week that a rural northwest Missouri prosecutor had in March 2012 dropped charges of sexual assault and exploiting a minor against two 17-year-old boys accused of plying a 13-year-old girl with alcohol and recording her alleged rape.

Some top Republican officials clamored for Koster to intervene. But Koster said he could do nothing unless the local prosecutor asked for help or stepped aside so that a special prosecutor could be appointed. Ultimately, Nodaway County Prosecutor Robert Rice did ask a judge to name a special prosecutor to take a fresh look at the case.

Only then did Koster release a written statement saying he “stands ready to assist” in a “prosecutorial review.”

In some states, such as Alaska, Delaware and Rhode Island, the attorneys general have original jurisdiction in all criminal cases, according to the National Association of Attorneys General. But in Missouri and many other states, the discretion to file and dismiss most criminal charges rests with local prosecutors.

In Missouri, there are 115 local prosecutors, and no one to veto their decisions.

“There is an ongoing debate historically about whether the attorney general should have some sort of authority to step in or overrule a prosecutor,” said Chuck Hatfield, a former chief of staff for Koster’s predecessor Jay Nixon, who now is governor. “But I’m not aware of any law that allows that — and that certainly has not been the practice.”

A Missouri law dating to at least 1939 allows the governor to direct the attorney general to aid a local prosecutor. But Nixon spokesman Scott Holste, who also served in the attorney general’s office, said that law “is predicated on that request” for aid coming from a local prosecutor.

Rice did not make such a request in the sexual assault investigation.

Jason Lamb, the executive director of the Missouri Office of Prosecution Services, said he’s not aware of any figures about how often prosecutors recuse themselves or seek help from the attorney general. But it’s not uncommon when cases are controversial or pose potential conflicts of interest for local prosecutors, he said.

The notion that decisions by locally elected prosecutors cannot be overridden “has been a longstanding principle of criminal justice in America,” Lamb said.

“What you don’t ever want with any system of justice is the idea of trying to shop for justice,” Lamb added.

Koster is a former Cass County prosecutor and state senator who plans to run for governor in 2016.

Two Republican lawmakers interested in succeeding Koster have suggested that he could have interjected himself into the Nodaway County case, even though no state law gives the attorney general specific prosecutorial powers for alleged rapes.

State Sen. Kurt Schaefer, a Columbia lawyer who recently announced his 2016 campaign for attorney general, suggested Koster could have used a 2009 law to conduct his own investigation of the matter.

That law allows the attorney general, working through the local prosecutor in Missouri’s capital city, to ask a judge to issue subpoenas for witnesses and information to be submitted to the attorney general’s office regarding sexual and pornographic offenses. The attorney general then can review the evidence and, if he believes a criminal violation occurred, submit it to the local prosecutor. But there’s a catch: the attorney general can only use such powers when there is a question about the venue where the alleged crime occurred.

Schaefer said that because one of the teenagers allegedly made a cellphone video of the sexual act, that video may have been shared with people in other counties and Koster could have cited venue uncertainties as grounds to investigate the case.

“This absolutely needs a fresh set of eyes to look at it,” Schaefer said.

House Speaker Tim Jones, a Eureka lawyer contemplating an attorney general’s bid, suggested Koster could have intervened under a state law that describes the attorney general’s power to represent the state. That law refers to civil lawsuits and other proceedings necessary to protect the state’s interests — not specifically to criminal prosecutions.

But Jones said “it’s arguable that section gives the attorney general broad latitude.”

“Perhaps we have found an ambiguity in the law that we need to have debated next session,” Jones said.