It's the last dance with Mary Jane for states that had been illegally allowing food stamp recipients to claim deductions for medical marijuana. 

The Department of Agriculture last month sent out a memo ordering states to stop permitting the practice. Though 18 states currently allow medical marijuana use in some capacity, it remains illegal under federal law. 

And until recently, at least a few states were allowing food stamp users to deduct the cost of their medical marijuana in order to meet the income eligibility requirements. 

For instance, a family of four under USDA guidelines must earn less than $1,863 a month to qualify for food stamps. In limited cases, families were deducting the cost of their medical marijuana every month to bring their monthly income within that limit. 

That's a no-no, Lizbeth Silbermann, director of the USDA program development division, wrote in the memo last month.