There are zero precedents under the equal protection clause that do anything like what the link suggested. On top of that the equal protection clause by its terms doesn't even apply to the federal government, since it is situated in the fourteenth amendment. It has been reverse incorporated via the fifth amendment due process clause, but again never in any case remotely like what is being suggested. You can't just look at the words "equal protection" and start extrapolating wildly. That's not how these things work.

There are several memorandum from office of the Attorney General that state Justice Department policy as to where efforts should be focused (e.g. https://www.justice.gov/iso/opa/resources/305201382913275685...) and even before that the federal government tended not to exert a lot of effort on small time marijuana users. But it is emphatically not the case that "personal possession ... is completely legal under federal law".

Please do not spread this type of misinformation, it can be have enormous consequences.

Pot isn't legal in DC. It's still against federal law everywhere in the US.

Not that Congress actually has the power, under the constitution, to make possession illegal. But that boat sailed long ago.