[FOX_111]

Generally, the fps limit is set in order to have 1j at impact.
1 joule is a general tested limit at wich the skin break. 1 joule is equivalent of putting a 280fps (old school stock AEG) at point blank with 0.20g on your skin and firing. It will hurt like hell, make a red welt, maybe even bleed a little, but that it.

So large open field with longer engagements distances allow 400fps. CQB field with closer engagement distances allow up to 350fps. That to mitigate injuries.

Snipers MED (minimum engagement distance) are set to have 1 joule at impact, using apropriate ammo. So a sniper chronied at 450fps (with .20g BB), firing a .30g BB with have a MED set at 40 feets. Inside that distance, the BB impact energy will be above 1 joule.

Just to clear things up, fps limits set on fields are for safety.
Fps limits sets by the border agency are for bullshit. I mean, to fall inside the regulations of what they beleive an unrestricted airgun should be.
Fps limits set in the criminal code are to define what a firearm is.

3 differents points of views for different goals. When playing, worry about field limit. When importing, worry about importation laws. When in trouble, talk to your lawyer about criminal laws.