Most european countries have sodium nitrite restrictions on its usage because of common trading laws in europe, since theyre generalized: this product is hazardous, highly toxic and explosive. I even think theyre trying to ban its usage altogether lately due to its usage for suicides, at least where i live they are trying. Labs, butchers and other businesses can get it. But civilians can't. Now the laws are lax from one country to another. I think spain, poland are the countries the most lax on SN purchase. Maybe there are others though, idk.
That's specifically on europe, though i don't know how legislation works outside of the european continent.