I remembered that ban too and found this online:
In mid-2003, due to cross-contamination at a Madison, Wisconsin-area pet swap from an unquarantined Gambian pouched rat imported from Ghana, several prairie dogs in captivity acquired monkeypox, and subsequently a few humans were also infected. This led the CDC to institute an outright ban on the sale, trade, and transport of prairie dogs within the United States.[18] The disease was never introduced to any wild populations. The European Union also banned importation of prairie dogs in response.[19] While largely seen by exotic pet owners[who?] and vendors[who?] as unfair, the monkeypox scare was not the only zoonosis incident associated with prairie dogs.[citation needed]
Prairie dogs are also very susceptible to bubonic plague, and many wild colonies have been wiped out by it.[20][21][22][23] Also, in 2002 a large group of prairie dogs in captivity in Texas were found to have contracted tularemia.[24] The prairie dog ban is frequently cited by the CDC as a successful response to the threat of zoonosis.[citation needed]
Prairie dogs that were in captivity at the time of the ban in 2003 were allowed to be kept under a grandfather clause, but were not to be bought, traded, or sold and transport was only permitted to and from a veterinarian under quarantined procedures.[citation needed]
On September 8, 2008, the FDA and CDC rescinded the ban making it once again legal to capture, sell, and transport prairie dogs effective immediately. Federal Register / Vol. 73, No. 174 Although the federal ban has been lifted, several States still have their own ban on prairie dogs in place.[citation needed]