Working in an Amazon warehouse is physically demanding. It generally doesn't pay much. And yet the company has tried to squeeze even more uncompensated time from its employees, according to workers involved in a case that was heard by the Supreme Court last week.

Not surprisingly, the very pro-business Supreme Court appears likely to take the company's side. But what is surprising — and dismaying — is that the Obama administration's Department of Labor is siding against the workers, too.

The case, Integrity Staffing Solutions v. Busk, concerns a lawsuit filed against a temp agency by workers assigned to Amazon. The workers allege that they were required to undergo a security process that took as long as 25 minutes after an exhausting 12-hour shift. Although the checks are mandatory, the temp agency refused to compensate the workers for their time.

The legal question in this case is whether the security check constitutes a "preliminary" or "postliminary" activity, or whether it is "integral and indispensable" to the job. If it's the former, federal law does not require workers to be compensated. If the latter, they must be paid for the time. The workers in this case argue that because the security checks were mandatory and done for the company's benefit, they were entitled to compensation. The 9th U.S. Circuit Court of Appeals sided with the workers.

Their argument is compelling. If tasks required by the employer for the employer's benefit are not considered "integral" to the "principal actives" of job, that would produce plainly illogical and unfair results. As an attorney for one of the plaintiffs argues, it would follow from this assumption that "if the company ordered an employee to mow the lawn outside the Amazon warehouse for 25 minutes after his 12-hour shift, the company would not have to pay for that work because it would not be considered 'integral and indispensable' to his principal activity of tracking down goods ordered online." This cannot be right.

Unfortunately, it seems likely that the Supreme Court will reverse the Ninth Circuit's decision. Justice Stephen Breyer, surely a vote the workers would need, explained to the plaintiff's attorney why he is likely to side with the temp agency (and, indirectly, Amazon): "I'm in the situation probably I'd say go with the Labor Department. They are the ones who are in charge of this. And they are saying you lose."

Breyer's remarks reveal a regrettable truth: The Obama administration sided with Integrity Staffing. Why would the government do this although the relevant statute certainly doesn't compel it to do so? The government's brief relies in part on a 2007 opinion by the 11th Circuit holding that airport workers did not have to be compensated for the time they spent going through a security checkpoint. That decision is reasonable, but differs from this case in two crucial respects: requirements to go through airport security checkpoints were not established by airport employers, and their primary purpose is to protect the security of passengers (as opposed to the interests of employers). The brief fails to account for these crucial differences.

The Obama administration is clearly on the wrong side here. The Department of Labor should interpret ambiguities in the labor law to guarantee that workers are fairly compensated, not to ensure that the labor expenses of employers are minimized. Amazon is already in a far stronger negotiating position than its workers and hardly needs the government to put its huge thumb on the scale.

As New York's Annie Lowrey observes, Amazon's determination to reduce costs benefits consumers, but it should not be allowed to do this at the expense of treating its workers fairly. New regulations will be needed to protect workers in a national environment in which most wages are stagnating or worse. It's unfortunate, given this necessity, that existing legislation is not being interpreted to protect workers from further exploitation.

If the Supreme Court rules against the workers, Congress should change the law to make clear that when employees perform mandatory tasks for the benefit of their employer, they should be compensated for their time.