From Wikipedia
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Although the federal government does not normally regulate air guns, some state and local governments do; the Law Center to Prevent Gun Violence has complied a list of states and selected municipalities that regulate air guns, finding that 23 states and the District of Columbia regulate air guns to some degree. Two states (New Jersey and Rhode Island) define all non-powder guns as firearms; two states (Illinois and Michigan) define certain high-power and/or large caliber non-powder guns as firearms; three states (Connecticut, Delaware and North Dakota) define non-powder guns as dangerous weapons (but not firearms). The remaining states which regulate air guns impose age restrictions on possession, use, or transfer of non-powder guns, and/or explicitly regulate possession of non-powder guns on school grounds
New York City has a restrictive municipal ordinance regulating air guns. New York state law prohibits anyone under the age of 16 from possessing an air gun. Air guns were previously banned in San Francisco, but a state preemption statute struck down the ban, and the San Francisco District Attorney declared them legal as long as in compliance with state law.
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Beyond that you would have to actually check each county/city ordinance before passing through them. As I have said, in my case here in Longmont, CO, any form of air gun (airsoft, or pellet) is 100% illegal in public while a proper gun is perfectly legal to carry into your local bank (which I do regularly). Since air-guns are not protected by the 2A, they are the perfect example of what "common sense gun laws" (ie ban) would look like if we did not have that protection (and organizations like the NRA).
