A new Rand Corp. study of the federal law designed to protect members of the National Guard and Reserve from discrimination when they return to the workplace finds that employers have “incomplete” knowledge of the law.

One-quarter of those who employ citizen-soldiers admit they don’t have all the information they need to comply. The law is known as USERRA, the Uniformed Services Employment and Re-employment Rights Act. It has come under greater attention as a larger number of Guard and Reserve units have been called to active duty.

While the number of Reserve units ordered to active duty is likely to decrease, the impact of USERRA remains. The Pentagon’s long-term strategy is to use Guard and Reserve units as operational forces who can expect to be deployed rather than the traditional “weekend warrior” duty.

The Rand study said legal protections under the act are consistent with other employment law but that understanding how it works and where to go to for support is lacking. There was no consensus on whether longer or shorter absences would be beneficial to employers.

Schools, businesses that depend on personal relationships with clients and businesses that rely on highly skilled or trained employees are more likely to experience problems with absences and need more advance notice, the study found.

The study did not look at how well USERRA works when an employee reports a problem. The Star Tribune last year examined how USERRA is enforced and found that it is often a time-consuming venture that produces disappointing results. In Minnesota, if a service member filed a complaint with the U.S. Department of Labor, the claim was dismissed as having “no merit” more often than it was settled or granted.

The Washington Post reported last year that the federal government, the largest employer of citizen soldiers, is the biggest law breaker. In fiscal 2011, more than 18 percent of the complaints involved federal agencies.