I got curious and tried to find out. This is what I came up with, from a Glock site. (
http://www.glockfaq.com/models.htm)
To qualify for import a pistol must score 75 points based on the following system:
Characteristic Points
Length: for each 1/4" over 6" 1
Forged steel frame 15
Forged HTS alloy frame 20
Unloaded weight w/mag (per oz.) 1
.22 short and .25 auto 0
.22 LR and 7.65mm to .380 auto 3
9mm parabellum and over 10
Locked breech mechanism 5
Loaded chamber indicator 5
Grip safety 3
Magazine safety 5
Firing pin block or lock 10
External hammer 2
Double action 10
Drift adjustable target sight 5
Click adjustable target sight 10
Target grips 5
Target trigger 2
For example, here is how the G17 scores: Length (7.28") 5
Weight (24.79oz) 25
Caliber (9mm) 10
Locked breech 5
Firing pin block 10
Double action 10
Target sight 10
Target grips 5
Total 80