If it is a technical means, it is under the purview of the FCC.
I am not aware of any action the FCC has taken against passive technical methods, such as Faraday cages. However, the FCC made clear in its finding against Marriott that it considered active technical methods to be "harmful interference" to the airwaves and therefore within the FCC's authority to fine.
Business arrangements, to be absolutely clear, are the authority of the Federal Trade Commission (FTC). Trade being synonymous with business in this context. The only reason the FCC claims any jurisdiction over ISP's (and WiFi operators are not presently considered ISP's, BTW) is because the FCC has classified them as Title II common carriers and therefore subject to different, special regulations. These are NOT the same regulations that dictate compliance for devices in the unlicensed spectrum (900MHz, 2.4GHz, 5GHz, 60GHz, etc.).
Seriously, read the NANOG thread. All your questions are answered there by very smart people with references to FCC publications.
To answer your simple question: No. The FCC does not have nor does it claim to have (at present) authority over commercial agreements between private parties, except under specific situations, such as Title II regulation. Your presence on someone else's property does not give you the right to use WiFi there. Period. It gives you a right to expect that your unlicensed wireless devices will not experience "harmful interference" which the FCC has to date only defined as active technical interference. You, however, may experience interference including being removed from the premises. That's not considered "harmful interference" by any definition that the FCC has been known to use.