Laura, it totally depends on your state's landlord tenant laws. In some cases the property owners may not be able to evict him simply because of a criminal past, and, if you are on a lease, his being there will not be considered a valid reason to break the lease. If he is breaking the law now, that's a different story. Out of curiosity what notice did you receive? Was it a meghan's law notification type of thing for sex offenders?
You might try posting at forum.freeadvice.com under the landlord/tenant law section. Be warned, the legal folks there are pretty snarky! You can usually get a good answer though. I found this myself, regarding Texas and felons, which leads me to believe that it is up to the individual landlord to decide:
"Private landlords can, and usually do, refuse to rent to felons. Even felons raising children are usually limited to the worst part of town to find an apartment because no other landlord will rent to them. No matter how long or how hard a felon works to improve his or her life, and no matter how many children depend on the felon for support, many felons must raise their family in substandard housing because of the label “felon”."
Sparrow
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in sideways, thoroughly used up, totally worn out, and loudly proclaiming ‘Wow - what a ride!’ — Peter Sage