The guy was going to report you because you can't transport the fish live from the pond.
It's gotten to be a nusance fish among other reasons; see below
Current Status of this Species in the Gulf of Mexico Ecosystem:
This species has been introduced throughout the Gulf of Mexico ecosystem through aquarium and fish farm releases and for weed control by the Florida Game and Fresh Water Fish Commission (Buntz and Manooch, 1968; Courtenay and Robins, 1973; Courtenay et al., 1974; Hogg, 1976). It has also been continually stocked in Alabama by state fisheries agencies for possible use in aquiculture and to control filamentous algae growth, but appears unable to survive the winters (Smith-Vaniz, 1968; Habel, 1975). The source of introduction of blue tilapia in Texas is unknown (Hubbs in Hubbs et al., 1978), although Howells (1992) suggested they were introduced through fish farm and bait bucket releases.
Blue tilapia are presently wide spread in Florida and Texas, and are continuing to expand their range (Courtney et al. 1991). At given localities they have become the predominant fish, especially in eutrophic waters and near thermal refuges (McBay, 1961; Buntz and Manooch, 1969; Courtenay et al. 1974; Noble et al. 1975; Hogg, 1976; Hubbs et al., 1978). Populations appear commonly to made up of few large individuals rather than many small ones, which make this species especially important in terms of biomass (Shafland, 1996). Noble et al. (1975) reported O. aureus as the most common species in Trinidad Reservoir, Texas, before it was eradicated (Courtenay and Shauffer, 1984). Hubbs et al.(1978) also reported this species as possibly the most abundant species in Braunig Reservoir, Texas, out-competing hardy native species such as the gizzard shad. Buntz and Manooch (1969) reported that by 1969, blue tilapia compromised up to 40% of the harvest of Lake Parker, Florida, and Williams in Courtenay et al. (1974) reported that it had increased to 69% of the total biomass of Lake Parker by 1972 and compromised over 93% of total biomass of Lake Effie, Polk county, that same year. Shafland (1996) reported blue tilapia commonly exceed 20% of the total fish biomass throughout much of south and central Florida.
Although blue tilapia are tropical fish, they have a greater tolerance of cold waters than do most other non-indigenous cichlids, which give them the potential to expand their range throughout the entire state of Florida, and to wider areas of Texas and other Gulf States than could most other tropical cichlids (Shafland and Pestrak, 1982).
Potential Impacts:
Blue tilapia are one of the most common non-indigenous fish of the Gulf drainages, and the dominant species over much of their range. Native fish assemblages appear unable to control blue tilapia numbers either by competition or direct predation (Buntz and Manooch, 1968). Zale and Gregory (1990), reported overlap in diet of introduced juvenile blue tilapia with juvenile shad (Dorosoma spp.), and suggested competition for limited trophic resources, as a possible reason for the decline of local populations of shad in Florida. Buntz and Manooch (1968), reported competition in Florida between Blue tilapia and native centrarchids for breeding areas by adults, and trophic resources by juveniles. Besides directly competing for nesting areas with native fish, their aggressive behavior probably alters community structure where they are abundant (McBay, 1961). Noble et al. (1975), reported inhibition of largemouth bass breeding in the presence of high densities of blue tilapia, in the eutrophic waters of Lake Trinidad, Texas. The blue tilapia has undoubtably displaced many native fish and contributed to lowering local biodiversity where common.
Laws pertaining to :
http://fac.dos.state.fl.us/faconline/chapter68.pdf
List of exotics in FL.
http://myfwc.com/fishing/fishes/non-native.html
Tilapia are a very interesting fish to keep, especially the mouth brooders.
There are alot of exotics out there that would be great to keep, Just seems some people can't keep their fish in their pants and ruin it for others.