> Jammers like this in the US (and apparently from this article, other jurisdictions) are illegal if their effect reaches beyond your property since it can block access to emergency services, etc. I think RF containment is a legally-safer strategy.

Without commenting on the legality of your RF containment idea, it's worth noting that jamming is also illegal in the U.S. even if confined to your own property. The Communications Act, 47 U,S,C, 333, prohibits causing "willful or malicious interference" to a radio licensee categorically, regardless of where it occurs. That is why the FCC fined Marriott Hotels $600,000 for operating a jammer[1] at their own resort property. https://docs.fcc.gov/public/attachments/DA-14-1444A1.pdf

[1] The FCC treated it as a jammer, so the example applies for illustrating the scope of 333. But it's worth noting out of interest that, in this case, Marriot was transmitting Wi-Fi deauthentication packets to keep people off of private AP--presumably in an attempt to force conference attendees to pay for the resort's Wi-Fi service. Regardless, the FCC concluded that this constituted willful interference.

Edit: It would be more accurate to have said that the FCC treated Marriott's behavior in that case as causing "willful interference." The actual feature of the equipment that they used (which I think was a standard enterprise Wi-Fi AP) has other legitimate uses. She FCC did not say that the equipment itself was a jammer across the board.