In the words of Karthik https://vexforum.com/t/answered-possessing-opposing-mobile-goals/41460/1

Make a wallbot that wraps around their mobile goals and their stationary goal and they can’t score anything. If you want to be sure, add some claw or lift to block access to their stationary goal and let you do a bit of scoring on your own. @Carl @Barin

Yeah, I was pretty sad to see that they cannot be picked up, though. This idea is/was gonna be my next question now that the first one’s answered

Why would it need to be questioned? The only legal issue is how concave you can be around the goals right?

Well, by the previous rule there was no reason to believe you couldn’t scoop under the goal, but apparently they didn’t want to allow that.