||Consider if you suffer this kind of problem.
The local office of a company contracting him, cannot formally verified his work experience. I suspect this is caused by the chance that his employment can be used as a circumstancial evidence that the local office break some of its head office rules. The best that he can do is to have his supervisor (who is oficially working in this company) confirm the existence of his contract, or showing his paper contract if requested, or showing the documentation and revealing insider information of this project. Unfortunately, the last option is unethical and a serious violation of law. All of these options also requires an initiative from the company he applied to, to clarify his claim.
The circumstances concerning his work experience, which is a good indicator of the quality of his experience, won't be admitted by his supervisor since the experience hints serious local office violation of head office regulation. The customer of this particular project won't possibly verified this project because it's too scandalous.
In summary, his work experience is unverifiable. He will be considered liar if he mentions it.
Now, given all these problems, he'd rather omit this experience. But a quick google show that in some countries resume omission is considered lying.
A better way is probably to explain the circumstances of this experience. But concise explanation in resume is difficult. In addition, such explanation in a resume might immediately make him unqualified due to complication processing such application. And the third problem is such explanation will be considered outrageous given the credibility of this company in developed countries.
The best solution I found is to downplay this experience. But there is a reasonable chance that his experience might make regulators deem him uneligible to work in a certain field and location. In the future, he might need to refuse this certain responsibilities without able to explain to his new company why he refuse to take it. A possible fix is by not working in that particular field anymore, but is there a better solution?
Any suggestions? Thanks in advance.