thomas.loc.gov has the full text of any federal law you might want.
The specific statutes you want are the Electronic Communications Privacy Act of 1986 (ECPA) and the Telephone Disclosure and Dispute Resolution Act of 1994 (TDDRA). Actually, TDDRA might be a 1993 law that took effect in '94.
ECPA made it unlawful to monitor mobile radio telephone calls (among other things). TDDRA added cordless phones.
Indeed, true. It also required the FCC to enact regulations to prevent receivers being available to receive cellular frequencies. The FCC did that by codifying regulations that made it impossible to obtain type acceptance for radios capable of receiving cellular frequencies. Thus, the manufacture or import of such radios became a violation of those regulations.
For a short time, some manufacturers got their type acceptance by creating circuits that created a hardware block. I have a Pro-43 that was cellular enabled by removing a single surface mount diode on a corner of one of the circuit boards.
After a while, things tightened up and the regs required that for type acceptance, the radios could not be "easily modifiable" to enable cellular reception, or which could have the reception enabled through software download.
For a time, there was an exemption for "test equipment" to be sold strictly to "authorized" service and maintenance personnel, such as cellular radio technicians. Apparently at some point that was expanded to "legitimately authorized governmental users" of some sort. The exact wording suggests they were speaking about "government users" in the sense they talk about federal spectrum users (regulated by the NTIA and DOD rather than the FCC), but if they had any objection to local and state governments, they seem to have been rather quiet about it.
It's always fun to watch FCC regulations evolve.
There's a notation in the NTIA Spectrum Tables that cross-references a couple of 27.500+ frequencies that can be used by certain government allocations for itinerant use. And there's a footnote that notes that users of those frequencies should use a transceiver of the CB Radio Service which has type-acceptance.
Of course, there's another regulation elsewhere which says that radios which could operate on those frequencies could not possibly obtain type-acceptance in the CB Radio Service.
It's kind of fun when you get deep into this stuff.