Allowing states to control food stamp usage and decide whether to drug test recipients is part of Trump's larger plan to reform welfare benefits.
Unemployment insurance, welfare benefits, and food stamp usage are similar type benefits. As Dick Cheney once said about them:
"[P]ublic policy designed to help workers who lose their jobs can lead to structural unemployment as an unintended side effect. Most economically advanced countries provide benefits to laid-off workers as a way to tide them over until they find a new job. In the United States, these benefits typically replace only a small fraction of a worker’s income and expire after 26 weeks. In other countries, particularly in Europe, benefits are more generous and last longer. The drawback to this generosity is that it reduces a worker’s incentive to quickly find a new job. Generous unemployment benefits in some European countries are widely believed to be one of the main causes of 'Eurosclerosis,' the persistent high unemployment that afflicts a umber of European economies."
Wait! That was Paul Krugman in his Macro Economics textbook....
However, cue the Democrats' whinging about throwing people out of their homes and onto the streets to starve.
Link: https://books.google.com/books?id=BVOn0FX7iPAC&pg=PA210&lpg=PA210&dq=%22Public+policy+designed+to+help+workers+who+lose+their+jobs+can+lead+to+structural+unemployment+as+an+unintended+side+effect.%22&source=bl&ots=CYYpmyXR96&sig=3F73FRt44lndXW2TBzWdgdmsGp