It is US law. It has an FAA control tower at the airport and US aviation rules. The regs also says you have to register your drone if you will fly in any US territory (including Guam). The airport is Class D and it's airspace extends about 5 miles from its center. You would need permission to operate inside that area. Unfortunately that covers all of Tumon.
If you go to skyvector.com you can search for Guam and you can select the "Marianas Islands Inset" chart. Find the selection tabs at the top of the map. This will show the local aviation sectional chart. It is daunting for non-pilots, but just pay attention to the blue dashed circular line around the airport and the smaller gray circle around Anderson. You are not supposed to fly at all within those without permission. Also, hivemapper.com does provide some areas that seem to be restricted areas, like Navy properties, the prison, and several other areas. You are not supposed to fly in National Wildlife Refuges. As far as I know the only one is up around Ritidian Point. There are some US National Parks. Currently you may not takeoff, land or operate a drone while in the park. So you have to go to the National Park Service website, find the Guam map, zoom all the way in and find the real park boundaries. As far as I know you can be outside the park and fly the drone over the park and be legal.
I forgot to mention using the FAA's B4UFly app on your phone. It's the only app I have seen with all the restricted areas depicted on a map. There's quite a few areas restricted. AirMap is pretty good too. There is also a lot of nice areas not restricted. Most of Yona, Talofofo, Inarajan and Merizo not restricted. Sella Bay area is good. Up in Yigo is mostly restricted. And you could fly in Tumon or around Two Lovers Point, but you are supposed to get permission from the airport control tower first.
your screwed. talk to the faa, quartermaster, grounds keeper, staff sargent. as high a rank as you can get. the tower supervisor. then his boss.
maybe someone will answer a question with a usable answer.
but then guam is its own country, maybe some " other law apply's that could help?