Past achievements must never influence a sanction for illegal behaviour. You cannot accumulate legal goodwill that way. There's no rule of law if you could / can, for law simply doesn't recognise accumulated goodwill.
It only recognises jail time served innocently as accumulated goodwill, and only so to some extent.

I don't think bringing back some minor booty should be a major offence at all, depending on how it was acquired (battlefield pick-up of a Makarov being no problem, taking a golden Saddam gun from a pile of already captured guns is another thing).