Newly reelected Gov. Scott Walker (R-WI) wants to drug test food stamp recipients. That's not actually the states' call to make, and when Georgia tried to do it, the Department of Agriculture stopped them. But Congressional Republicans are trying to change the law to allow state drug testing. States are already allowed to drug test for welfare. But drug tests of any kind, used as screening mechanisms, are potentially unconstitutional.

The law around food stamps and drug testing now

Walker is not the first state leader to propose testing Supplemental Nutrition Assistance Program (SNAP, colloquially known as food stamps) beneficiaries. Earlier this year, Georgia enacted a law requiring testing in cases where there's a "reasonable suspicion" of drug use by the benefit applicants.

But the Georgia requirement was barred from taking effect by the US Department of Agriculture, which administers the program. Federal law "expressly prohibit[s] States from imposing additional standards of eligibility for SNAP participation," Robin Bailey, the regional administrator for the Southeast, wrote Georgia Human Services Commissioner Keith Horton. "Requiring SNAP applicants and recipients to pass a drug test in order to receive benefits would constitute an additional condition of eligibility, and therefore, is not allowable under law." The Georgia law was thus barred from taking effect.

Walker is well aware of this precedent, and when he floated this idea before the election, he conceded to the Milwaukee Journal-Sentinel, "We believe that there will potentially be a fight with the federal government and in court."

Congressional Republicans also want testing

In 2013, the House approved by voice vote an amendment to the farm bill that would reverse the statutes cited by Bailey and allow states to drug test SNAP recipients. The provision was struck in conference committee, and so never became law. But it suggests that Walker, Georgia Gov. Nathan Deal, and other Republican state-level officials attempting to drug test SNAP recipients have allies on the Hill.

Drug testing of people with past records is currently allowed

As part of the 1996 welfare reform package, people with drug convictions can be barred from receiving food stamps, a requirement which states can (and increasingly do) opt out of, in whole or in part. Many states modify the drug convict ban in various ways, including by requiring drug testing of beneficiaries with drug records.

Also due to welfare reform, states can require that recipients of Temporary Assistance for Needy Families (TANF), the cash assistance program usually just referred to as "welfare," be drug tested. That, in practice, creates another avenue by which SNAP eligibility can be restricted via drug testing. As explained in a Congressional Research Service report by Maggie McCarty, Gene Falk, Randy Alison Aussenberg, and David Carpenter, "SNAP state agencies may choose to disqualify a SNAP recipient who fails to perform an action required by another means-tested program, such as TANF. For example, a state that disqualifies someone from TANF (or another means-tested program) for not participating in or failing a drug test may also disqualify that individual from SNAP." But this only applies to ongoing SNAP cases; if someone who failed a TANF drug test in the past applies for SNAP, that can't, on its own, disqualify them.

There are constitutional problems with all drug testing for government programs

Civil libertarians and advocates for the poor often argue that drug tests constitute a search subject to the requirements of the Fourth Amendment. States can try to get around this, as Georgia did, by requiring a "reasonable suspicion" before a test can be conducted, but a number of statutes lacking such caveats have been struck down. In 2013, a Florida district court struck down a state law requiring drug testing of TANF applicants as a Fourth Amendment violation. A similar Michigan law was struck down by a district court, and then the 6th Circuit Court of Appeals, in the early 2000s.

Drug testing doesn't make much financial sense

One remarkable fact about the Florida program that was struck down is that, despite drug testing advocates' frequent appeals to budget savings as a rationale, it actually cost the state money. In the first few months of testing, drug tests saved the state $40,480 in denied benefits, but forced it to reimburse $246,050 to people who passed the tests.

Social policy experts also express doubts about the implied rationale behind welfare and SNAP drug testing: that recipients, or poor people in general, are likelier to abuse drugs. "On every measure we examine, SNAP recipients are only slightly more likely than non-recipients to display substance use disorders," University of Michigan's Sheldon Danzinger and University of Chicago's Harold Pollack write. "And some obvious socio-demographic subgroups display much higher prevalence of substance use disorders than SNAP recipients do." White men age 18-24, for example, were more than twice as likely to have substance use disorders as SNAP recipients.