Citation, please? This is an area of the law with which I'm not too familiar.
I do recall from dim memory that private-property rights aren't without limits. For example:
+ The (U.S.) National Labor Relations Act puts limits on an employer's right to prohibit employee collective action on the employer's property;
+ Similarly, various civil-rights acts prohibit the owner of a business from refusing service to people on impermissible discriminatory grounds (race, national origin, etc.);
+ [ADDED:] Anti-trust law places limits on a business owner's ability to say, for example, I'll sell you my patented photocopier only if you agree to buy all your unpatented paper from me as well.
[EDITED:] I'm not saying the first two laws apply in this case. I am suggesting that anti-trust law, and perhaps federal communications law, might analogously limit the ability of the owner of a business to require guests, as a condition of admission, to forego their lawful access to the public spectrum. That practice seems roughly analogous to the conference company saying, "you can attend our conference, but only if you travel to the conference center in one of the expensive private limousines that we've arranged for, instead of in a cab."