States Where Defensive Sprays are Restricted
New York and Massachusetts:  residents in those states can only purchase
defensive sprays from FFL dealers and licensed pharmacists.

Michigan: OC (oleoresin capsicum) defensive spray cannot consist of more that
2% concentrate.  CS (othoclorobenzalmalonitrile) is the only tear gas accepted
and cannot be larger than 35 grams per container.  All combination sprays are
banned.

Wisconsin: only pepper is allowed.  Tear gas, UV DYE and all combination
defensive sprays are banned.  OC cannot be more than 10% concentrate.  
Defensive spray containers must be between 15-60 grams as well as have a
safety feature.
The above list provides only basic information about pepper spray laws within the U.S.  
Ultimately, it is up to the customer to know the laws and restrictions within his/her state,
county and city.