Prealongus, I agree with you 50:50
I do believe that genetic mixing between previously isolated and genetically differentiated populations can become a problem, and as hard as it may be to believe, have never kept a species that did not naturally occure in the region I lived in (not through choice, mind you, it just happened that way). Ive done advanced conservation genetics courses and understand the problems (although it is more of a problem for actual species conservation rather than ecosystem functioning, as hybrids between races will continue to have basically the same ecological niches and roles)
However, I don't think legalisation of corns (drugs are bad, mmmmkay?) is the way to gain greater control. People who have them will smell a rat and simply not register them. Take a look at the firearm situation. I know of many people who never registered their guns, handed them in, or sold them on when required to do so by the laws brought in after 1996. why? simply cause they knew they were backing themselves into a corner by letting the government know what they were doing (not because they are gun-runners intent on making a fast buck and destroying society as we know it). And on that note, they were right, because now firearms are so heavily regulated its not funny (not saying this is a bad thing, thats a whole other debate).
I know what you mean about the govt only identifying a problem when it is basically too late, but that is the reason we need to be keeping note of what is going on around us...and one of the reasons sites like this are so good. It comes down to everyone who in interested and knows enough to report anything unusual, etc (corn snakes in the local park, etc), otherwise the govt. will never notice anything.