Ketamine is schedule III in the US. That makes it less restricted than meds like adderall and most prescription opiates. Decriminalizing it wouldn't really matter for research studies.
I was recently surprised to learn about how big of an industry already exists around ketamine therapy. A search in your area (if in the US) would likely turn up several clinics nearby.
again, if drugs is what you need to "treat" depression then you probably have a much bigger problem in life that needs to be addressed rather than looking for another band-aid. depression is not some random disease you catch like a bad cold, it stems from personal or systemic issues that will only continue to feed into said depression until fixed.
Can you imagine how idiotic someone would sound if they were saying that about type 1 diabetes, or maybe schizophrenia?
Robin Williams lived a pretty pleasant life, but he died of depression. If Robin Freaking Williams couldn't beat it, what chance do the rest of us have for successful self-treatment?
It -can- be messed up brain chemistry despite what all the "only therapy helps" folks who are out to make a buck and prevent people from at least trying it.