It's alright if it's packaged as flour, but you could get in trouble if it's in a plastic bag.

Here's South Carolina's law (it's the first one I found on Google):

SECTION 44-53-390. Prohibited acts C; penalties.

(a) It is unlawful for a person knowingly or intentionally to:

...

(6) distribute or deliver a noncontrolled substance or an imitation controlled substance:

(A) with the expressed or implied representation that the substance is a narcotic or nonnarcotic controlled substance, or with the expressed or implied representation that the substance is of such nature or appearance that the recipient of the distribution or delivery will be able to dispose of the substance as a controlled substance;

(B) when the physical appearance of the finished product is substantially similar to a specific controlled substance, or if in a tablet or capsule dosage form as a finished product it is similar in color, shape, and size to any controlled substances' dosage form, or its finished dosage form has similar, but not necessarily identical, markings on each dosage unit as any controlled substances' dosage form, or if its finished dosage form container bears similar, but not necessarily identical, markings or printed material as any controlled substances which is commercially manufactured and commercially packaged by a manufacturer or repackager registered under the provisions of Title 21, Section 823 of the United States Code. In any prosecution for unlawful delivery of a noncontrolled substance, it is no defense that the accused believed the noncontrolled substance to actually be a controlled substance.