Did they exist before the armistance with Cyrodil? Cause you know, it doesn't seem to me like the Telvanni would be the kind to enforce laws unless they had to. There's probably no anwer for this, but it's just a bit of random curiosity.

Everybody has to enforce laws, even the Telvani. Perhaps not imperial law but Dunmeri law or at the very least Telvani law.

It's not written I believe, but it's just with some common sense every province/city and such more or less needs some kind of enforcers, otherwise it would be chaos.

Yeah, I figured as much. Still, the Telvanni are the most chaotic organization I've seen in Tamriel, so I thought I'd go ahead and ask anways.

I must agree there, but you can see Telvanni "enforcers" in Morrowind.

There are Telvanni guards just like there are Redoran and Hlaalu guards. Heck, even the Skaal have guards.

And do you really believe the Telvanni wouldn't have their own laws anyway? They use a lot of slaves, have you ever heard of a slave-using culture that had absolutely no sort of repression force to make sure the slaves don't escape?

Before political confrontation Telvanni used http://www.imperial-library.info/mwbooks/affairs_of_wizards.shtml for guard duties, I guess they had someone else for special "chores" as well.
Therefore, (exclusively)Telvanni guard is relatively new force - less than 30 years.