Are you sure? That may be state- or case-specific, he might still be able to. I've worked with guys on probation and parole (from both Federal and State) before and usually the P.O.'s prior approval is all that's required, plus whatever hoops the P.O. has them jump through. He'd just have to work on it in advance--getting approval can take a while. No haz-mat or Canada runs, though, that I've heard of.
Like other people have said though, best bet is probably Mom & Pop places. Especially if you can present yourself well in person; that's about the only reason the guys I knew were hired. Two of them actually were hired on as equipment operators (just a forklift or bobcat) or general laborers at a waste transfer station/recycling center and worked up to driving truck (already had their CDLs before they started) a few months later after the owner trusted them a little more. Might be worth looking at...