It depends. I mean you cannot lump ALL "smart drugs" into one category. The term Smart Drug is a very loose interpretation.
I have brought Piracetam and Hydergine across the border, and had it fully inspected, with no problem at all.
However even THAT does not mean anything factual. Frankly the ability to bring something across the border is maybe 70% law and 30% The Mood Of The Agent.
I even brought Clen across once and had it serached and they saw it and let me keep going.