As much as we understand the need for preventing people from attempting to portray thier pets as service animals in an attempt to bring them with wherever they go, I believe that forcing centralized certification/registration would impose an undue hardship for many of those who are in legitimate need of the assistance that a SD can provide.
I got into training service dogs because of the near insurmountable obstacles that a person close to me was encountering in a small community when trying to resolve her need for a service dog. This community had NO public transportation, and the only few trainers in the region were more than willing to train someones animal to do service work, at a cost of thousands of dollars for that said labor. ( "Oh you are handicapped? yes I can train your dog to be a certified SD at 50 dollars an hour in *your own home*!" doesnt matter if you are on a fixed income, you could raise the mere few thousand easily by collecting cans or such, (yea do the math sometime to see how many cans would it take to raise 5 thousand dollars, its a LOT of cans! more than most handicapped people could easily accomplish hauling home from bins in front of stores (if others didnt raid the bins first, let alone picking up by ones self)
I would compare nationalized certification of SDs to attempting to make people install limiters (governers) into their cars that would prevent them from driving over the speed limit and prevent them from parking badly and parking in no-parking zones. in order to prevent the percentage of bad eggs that break the laws, or just do what they do in bad method what you really do is inconvienience the innocent to attempt to thwart the real wrongdoers that will invariably find another workaround.
I would also suspect that people would learn to forge SD certifications in a very short period of time ( for example a few months ago I discovered the evidence of a ring of college students that had been forging "21year old" drivers lisenses for underage students....they were incredible quality, could easily pass for legit, even had UV holograms, I knew they were faked because I found the 4 color badgemaker tape with student IDs mixed inbetween different states IDs, passed it on to the DMV and they picked up the kid who sold me the printer )
I do know there are many people out there with legitimate needs of properly trained Service animals that are attempting to use improperly trained animals to fulfill those roles that need addressing as well... (one horror story I heard last week from another trainer was how she witnessed seeing a woman in a wheelchair in a store using an electric collar on a misbehaving dog in a SD vest while it screamed in pain, she shoulda been wearing the coller and let the dog carry the remote... ) but I dont think that imposing forced certification will cure the problem without imposing an unfair amount of inconvienience to the ones who do not deserve to be inconvienienced. One time or even yearly testing may or may not weed out problematic SD partnerships, willing education is probably the best approach
The problems of funding such nationalized testing sites and certification testing would have to be at the federal level, and then who would pay for the supplemental training needed for the "qualified disabled individuals" as well as for those whose animals required "more" training? how would standardization be acheived? one tester may be more easy, than the next, and heaven forbid you ever gacve a tester a reason to dislike you (I once had an argument with a DMV clerk over how he didnt like my signature, insisted I use a different one that was "more cursive" that I could never duplicate well, to this day I use the third variation that is my initials in a doctor-esque scribble, couldnt imagine if he was SD tester...)
In a best case scenario most individuals would have easy source of public transportation to get to their respeective testing facilities and everyone would pass the first time, not having to retrain in order to retest. a worst case scenario would be countless dollars spent fightings pro-bono lawsuits filed on the behalf of individuals who lost their ability to use the animal they had been using successfully for the last few years. individuals who "had" a SD that found out that their SD failed by one or two points out of a hundred would suffer untold grief.
IN ESSENCE: *AS* a service dog trainer, I see national certification testing to primarily be beneficial to the dog trainers who would have governamt jobs created for them by this requirement, Trainers who would have to sign off on who had trained said dogs and beneficial to the lawyers that would be employed fighting the inevitable suits, not the individuals.
yes it could in the long run make its easier for the few who could ride out the problems of instituting these programs, but it would be expensive and inconvieniencing to those who have a hard enough time as is just trying to live a somewhat normal life.
I suggest instituting a punishment program rather like house arrest for those who are found to be guilty of illegally using benifits intended for the handicapped. pretend like you are handicapped, get busted for passing "piddles" or "poopsie" off as a SD and spend a month with house arrest ankles/boots assigned to a wheelchair 16 hours a day...go to and from work IN A "special" WHEELCHAIR...go to the store, try to live a "normal life" while wearing a shirt and having the wheelchair prominantly labeled as " I am not really handicapped, this is court ordered because I faked being handicapped" - THAT would fix many fakers.