Yeah, I don't think there is a law that limits G's, though in Jersey there is a law, but it takes into account the max G's and the time you are subjected to them, The highest G's I can think of are Dreier Loioping (now in mexico) and Mindbender in Edmonton which are basically clones of each other which top out around 6.5 G's.
I think at SFGAm the highest G force probably occurs for a split second on Demon, entering the loops quite suddenly. Nothing at SFGAm is unusually forceful. I think the highest G force for the longest sustained time probably occurs on Goliath at SFMM or Titan at SFOT.
If I had to take a shot in the dark I'd say the highest peak of G force probably occurs during rough points on the large Arrow Loopers, I'd guess there is a split-split second on a few that probably gets you up to probably 30-40 G's. Keep in mind though that jumping into a chair subjects you to around 40 G's for a fraction of a second.
Favorite Wood Coasters: The Voyage, Ravine Flyer II, Thunderhead, Balder
Favorite Steel: Voltron Nevera, Steel Vengeance, Expedition GeForce, Olympia Looping
Parks visited: 232, Coasters Ridden: Steel: 894, Wood: 179, Total: 1073