Sure. The short answer is that there's no such thing as a "mod block." A block is the same whether it comes from a mod or not. (Longer answer: it's the sysop bit that gives you block power. For instance, if you had a mod bit but no sysop bit, you couldn't actually issue blocks or unblocks. More info can be found at Special:UserGroupRights.
Mods can give and remove the sysoprevoke bit, which prevents the user from exercising any sysop powers.)