The term "firearm" is defined in the Gun Control Act of 1968, 18 U.S.C. Section 921(a)(3), to include "(A) any weapon (including a starter gun), which will, or is designed to or may readily be converted to expel a projectile by the action of an explosive; (B) the frame or receiver of any such weapon...."
Based on Section 921(a)(3), air guns, because they use compressed air and not an explosive to expel a projectile, do not constitute firearms under Federal law — unless they are manufactured with the frames or receivers of an actual firearm. Accordingly, the domestic sale and possession of air guns is normally unregulated under the Federal firearms laws enforced by ATF.
Although the federal government does not normally regulate air guns, some state and local governments do; the Law Center to Prevent Gun Violence has compiled 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; one state (Illinois) defines 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. 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 they are in compliance with state law.
Along with state laws, local county laws or ordinances may be relevant to users of air guns. Generally, state laws do not mention air gun laws, but local counties do.
Although additional regulations exist, non-powder gun regulations can generally be broken down into the following categories:
Defining All Non-powder Guns as Firearms: New Jersey and Rhode Island take this approach, which generally ensures that all non-powder guns are kept out of the hands of children (absent direct adult supervision) and that people convicted of felonies and other individuals prohibited from possessing firearms are similarly barred from possessing non-powder guns.
Treating Certain Non-powder Guns as Firearms: Illinois and Michigan define high-power and/or large caliber non-powder guns as firearms. Illinois excludes from the definition of firearms non-powder guns of .18 caliber or less and non-powder guns with a muzzle velocity of less than 700 feet per second. Michigan excludes the following non-powder guns from the definition of firearms: smooth bore rifles or handguns designed and manufactured exclusively for propelling BBs, not exceeding .177 caliber by gas or air.
Defining Non-powder Guns as Dangerous Weapons: Connecticut, Delaware, and North Dakota list some or all non-powder guns as dangerous weapons. However, dangerous weapons laws tend to be much less comprehensive than laws regulating firearms. In Connecticut, it is unlawful to carry a dangerous weapon, although various exceptions exist for BB guns. It is also unlawful to transport a dangerous weapon in a vehicle without a permit. Delaware prohibits possession of dangerous weapons, which are defined to include certain large caliber BB or air guns. North Dakota applies enhanced penalties for the improper use or possession of dangerous weapons.
Regulating Non-powder Guns with Respect to Minors: Most states that regulate non-powder guns do so by prohibiting transfers to children or by prohibiting or limiting where the guns can be possessed or used, although the restrictions are often inapplicable with parental consent or adult supervision. Depending on the state, the term “child” is defined as being anywhere from under 18 years of age to under 12 years of age. A number of states also criminalize the use or possession of non-powder guns on or near school property, or provide that such use or possession shall be grounds for expulsion.
The Bulldog is also subsonic, so generally a bit louder than a .22 long rifle, and less than the average 9mm pistol. Louder than you want to just be firing off in your backyard suburban home, regardless how careful you are.
However, today - in the states aGun's are legal, SO IS MODERATING (suppressing) the sound! The DonnyFL Ronin works very well, but the Emperor works even better - quieting it down to about the sound of a standard pellet gun. I'm sure DonnyFL can help steer you to more specific answers, or a better place to get the answers.
Currently, to the best of my knowledge, AIR GUNS, like cross bows and black powder weapons, are legal (in 45 states) for ex-felons off parole, and living legally, that don't otherwise have a weapons limit or restriction, Big Bore air guns are still classed as a 'dangerous' and 'deadly' WEAPON... and often carry a harsher penalty IF ONE COMMITS A CRIME WHILE USING ONE OF THESE type of weapons. So, be aware... and educated!
DISCLAIMER: I'm NOT AN ATTORNEY, nor am I giving you any legal advice, so you'll need to keep up with ALL THE LAWS, rules and regulations, in your state, county, and city yourself... and consult an attorney or professional if necessary. (and your own country, if not the USA).
NOTE: All laws are subject to change, but to the best of my knowledge... this is where things are today, but ultimately, I'm NOT RESPONSIBLE FOR YOU - your choices, or actions! Dang sure don't have any control over the laws, regulations, or policies of any government agency, nor am I affiliated with any. So, CHECK THE LAWS THE EFFECT & IMPACT YOU & YOUR LIFE!