GL can be looted in the city. But non-GM have an extremely low chance looting GL. GM have higher chance of looting one. I looted a HK69 off a Giant Spider. That shows that non-GM have the chance of looting one.

( My previous post of looting GL has been updated into this post. I deleted my last post because it's wrong. Non-GM has a low chance of looting a GL. But not impossible)