Apple has found itself in the midst of an unexpected controversy this week after it was revealed that the iPhone maker bars laborers with recent felony convictions from working on its new corporate campus, a practice that may be unusual among private companies, but is not without precedent.

Construction workers who have been convicted of a felony within the past seven years are banned outright from the project, according to the San Francisco Chronicle, while those whose convictions are over seven years old are allowed. If the worker has been charged with a felony but not yet convicted, their eligibility is evaluated on a case-by-case basis.

This policy, which was apparently implemented in January, has reportedly affected "fewer than five" workers.

Labor leaders have panned Apple's approach, calling it "disturbing" and "antithetical to all the work that so many have been doing in recent years to lower California's recidivism rate." Others, like Calif. State Sen. Mark Leno, acknowledge that there are some situations in which past legal troubles might matter, but call on Apple to relax its restrictions in this scenario.

"There are certain positions where there is some nexus between the crime committed and the position offered. Construction does not appear to be one of those," Leno said. "In this situation, I would strongly suggest that this policy be changed."

Apple has long been known as one of the most secretive companies in the world, perhaps more so even than defense contractors. While prohibiting felons from construction employment may seem unusual for a company like Apple, it's actually a common practice for the likes of Boeing or Raytheon.

Many federal construction contracts, or contracts for private corporations working on behalf of the government, have even more stringent requirements. They often stipulate that a federal security clearance is a prerequisite — Â while this does not automatically disqualify applicants with felony convictions, they do face a much steeper path to employment.

Numerous examples of similar hiring practices can be seen on online job searches, particularly those that cater to individuals who already hold clearance. This posting from Caddell Construction, for example, seeks workers with "a minimum secret security clearance" to take on duties including concrete pouring, asphalt paving, excavation, remodeling, roofing, metal building construction, ceramic tile and flooring, plumbing and sewer repair, or landscaping.

That Apple has adopted this stance should not be a surprise to anyone who follows the company — its director of security operations is a former FBI special agent, and its software security chief spent years as a cryptologist in the U.S. Navy before joining the NSA.

Campus 2 is designed to "achieve the security and privacy required for the invention of new products by eliminating any public access through the site, and protecting the perimeters against trespassers," the company wrote in planning documents, naming security as one of its primary objectives.

Apple's plans for the new campus even include strategically-placed trees and high earthen berms around the perimeter — Â topped with security fencing and cameras — Â designed to not only secure the area, but to block any view of the buildings from public property. Apple security personnel already patrol the fence line around the clock, a practice that will continue after Apple moves in.