In reality, neither is correct, or useful for analyzing language. In a case like regard as a verb or as a noun, and with various prepositions, I think there are several combinations that conform to most people’s idea of “correct” English, and several combinations that may be common in certain dialects, social groups, or even individuals.

When you are dealing with something like the internet, though, there is the problem of many anonymous authors and lots of genuine mistakes (typos or “thinkos”). That is, there could well be several common combinations involving regard which, if you ask the author to look back over their speech, they might say, “oh, now that sounds wrong to me.” On the other hand, there may be dialects or social groups, or just plain individuals, who really think something like “with regarding to” is correct. But unless you actually go out and find the person and observe how they usually use the phrase, you can’t really tell if a single instance is a “mistake” or if they really think it’s correct. But if they do think it’s correct, there’s no way to discount it.

A useful proxy for seeing if people really are just making mistakes is to see how often they occur. If you get tens or hundreds of thousands of hits on google, it’s probably legitimate, if non-standard. If you only get a few hundred, you could probably wave it off as a commonly-made genuine mistake (or, you can notice the domain names of the websites, to see if they are from non-English speaking nations; some sorts of very common errors, getting hundreds of hits, will only occur on, say, sites hosted in Germany or Russia).