David Wells writes on CT, after government service, and advocates an amnesty:https://counterterrorismmatters.word...eme/#more-1031

Why? In part:
Which is why now might be the time for governments to consider a more proactive approach to shaping the foreign fighter outflow – specifically through a foreign fighter ‘amnesty’ or plea bargain scheme. Its broad aim would be to repatriate those foreign fighters disillusioned with the jihadist cause and keen to return home, but prevented from doing so by fear of a long prison sentence or their inability to leave the Middle East.
(He ends with) But given the risk and resource implications of the status quo, even the removal of a small number of foreign fighters from the battlefield would be worthwhile. And with Europe and much of the West facing a generation-long struggle against this threat, any scheme that makes countering it easier is surely worth considering.
By coincidence the free e-journal Perspectives on Terrorism has an article, from a more academic writer, and the Abstract says:
This article considers the implications of criminalised Muslim Diaspora community members from the West travelling to the Middle East and becoming involved in the terrorist activities of the Islamic State (IS), and ultimately returning from whence they came. It also reflects on the differences over time amongst the profile of recruits that have taken place since the time of the Mujahedeen in Afghanistan, to the ascendancy of IS. Recent research indicates both terrorist and organised crime groups draw recruits from the same Diaspora communities, a position supported in this article. While the focus of law enforcement and media attention appears to be on the potential of Islamic State Middle East veterans committing terrorist acts in the West on returning from conflict zones, there may well be a pervasive danger of them bringing significant risk to their countries of origin through enhanced participation in organised crime. The views of a selection of recently retired police professionals were gathered, and were found to support concerns around this potential significant and dangerous outcome of homecoming foreign fighters.
Link:http://www.terrorismanalysts.com/pt/.../view/541/1073
I am skeptical any government could pursue an amnesty, even if they participate in organized crime. At least outsiders are giving the issues some thought.