If you want to see some primary sources concerning Iran-Contra, just lick onto my profile page and follow the links.
The main problem with Mena is that unlike Iran-Contra, there is not enough primary source documentation. A lot of the Mena scandal revolves around eye-witness testimony of some sorts, which can become very shaky without a good amount of primary source documentation.
Ollie North secured some monies from selling arms to Iran. He funded an operation with the CIA and a couple rogue CIA-company guys, to fly arms down to the Contras. The CIA-rogues hired the best pilot in the country for such missions, Barry Seal, who was under investigation from the DEA, to run guns to the Contras so long as he promised to quit selling cocaine.
Needing an airport to operate out of, the CIA called upon an old contact they had worked with in the past. While at Oxford, Clinton worked with the CIA to keep tabs on anti-war protestors and certainly had some old contacts.
Clinton, who has trouble saying no, goes along with it. Dan Lassiter, an old contributor to Bill, and an old cocaine supplier to Roger Clinton (and by some accounts the governor himself) gets in on the cocaine Barry is flying back with him. Asa Hutchinson gets reports from the DEA that there is a drug smuggler in his district. He launches an investigation, only it's a sham investigation that is quickly shut down.
Ollie does not like the reports he is getting back about the cocaine so he leaks a picture of Barry Seal to the news media. Coupled with a plane crash filled with illegal arms being flown to the Contras, it was time to close up shop. Clinton is 'informed' the project has been aborted, and oh, they need a favor.
The favor finds Bill Clinton offering one of his bodyguards a chance to make it with the 'company.' LD Brown, a Clinton bodyguard state-trooper flies to Mexico and assassinate one of the pilots, Terry Reed.
LD gets to Mexico and gets cold feet.
Clinton wants nothing to do with the program anymore but its gotten a little out of hand, what with Barry Seal being assassinated in Louisiana and the CIA-rogues looking to use Arkansas state troopers to carry out hits.
Lassiter or some member of the so-called Dixie Mafia continues the very lucrative drug run through Mena airport when the Ives boys stumble across a drug shipment that they should not have found. They are murdered and placed on the train tracks. The state medical examiner, a Clinton associate, determines that they 'fell asleep after smoking pot on the tracks.' (Arkancide.)
Clinton, at this stage is an up and comer in the Democratic Party, so when the Kerry (John Kerry, Senator) Committee came to town to check on 'Mena,' he magically received a clean slate as did the CIA. Case closed.