Almost every psychological drug is either the same as, or similar to, some substance in our brain. They generally work by increasing the supply of that molecule in our brain. However these drugs are in very low concentration in our bodies. If you had drugs outside your body at the same concentrations that they were in your body, it probably wouldn't be illegal. Or at least nobody would be able to prosecute you. That's cause it would take a real lot of effort to even figure out the drug was present, and it couldn't be used to affect someone mentally to a noticeable degree.
I agree that it's stupid that drugs are illegal. The war on drugs has done much more harm than good. But trying to say it's wrong that these drugs are illegal because they exist naturally in our bodies is intellectually dishonest. You are propping up a strawman argument to punch it down.
'However these drugs are in very low concentration in our bodies."
Interesting, to my knowledge this is not known, do you have a link. Because we know people can experience similar effects to dmt/5-MeO most commonly during deep meditations, fasting, dark room retreats and holotropic breathing.
DMT peak level concentrations (Cmax) measured in whole blood after intramuscular (IM) injection (0.7 mg/kg, n = 11) and in plasma following intravenous (IV) administration (0.4 mg/kg, n = 10) of fully psychedelic doses are in the range of ≈14 to 154 μg/L and 32 to 204 μg/L, respectively. The corresponding molar concentrations of DMT are therefore in the range of 0.074–0.818 µM in whole blood and 0.170–1.08 µM in plasma.
It's not hard to find. The concentration for an IV DMT dose is 1000 times greater than what is found in your body after you're high. And IV doesn't need to be nearly as concentrated as what you need to get high from, for example, smoking.
So if you took a regular, safe, DMT dose and diluted it a couple thousand times, I doubt you'd get arrested for it. But that's not going to get anyone high.
Really though this is just common sense. Concentrations of drugs within your body are going to be way smaller than what you need to get high off of them. That's just the way drugs operate.