NEW YORK (MainStreet) – When you’re an employer looking to hire or fire, certain criteria are off-limits.

Under Title VII of the Civil Rights Act, it is illegal to discriminate against someone on the basis of race, color, religion, national origin or gender. Subsequent laws have prohibited discrimination based on age, sexual orientation, physical and mental disability, family status and veteran status. Together these constitute the protected classes, and federal law prohibits employers from discriminating on these criteria in hiring or firing or creating a work environment hostile to one of these groups.

There are exceptions, of course. According to the Americans With Disabilities Act, if a disability prevents you from performing the “essential functions or duties” of the job in question – say, if you’re a quadriplegic who wants to work as a welder on a skyscraper project – you’ll have a tough time arguing that the employer needs to accommodate you. But as a general rule, if you belong to one of the protected groups, employers will go out of their way to avoid the appearance of discrimination.

But such laws don’t protect the little guy – literally. Here are a few examples:

If you’re short.

A survey by the University of Pittsburgh found that tall students had starting salaries 12% higher than their shorter peers upon graduation. When such pay disparities are seen among protected groups, they often result in a lawsuit, as was the case in the massive Wal-Mart gender discrimination lawsuit just thrown out by the Supreme Court last month. But height is not a protected class on the federal level, so unless you live in Michigan – the one state that prohibits height discrimination in hiring – there’s not much you can do when you lose out on a job or promotion to a taller candidate. And while racist jokes in the workplace are likely to lead to a discrimination lawsuit for creating a hostile work environment, cracks about your height from co-workers don’t form the basis for litigation.

If you’re overweight.

Overweight Americans are similarly out of luck. The same law that makes height discrimination illegal in Michigan, the Elliott-Larsen Civil Rights Act, likewise prohibits weight discrimination, and last year a former Hooters waitress in the state filed a suit charging that she was placed on “weight probation” during her employment. But the growing number of obese Americans have no recourse on the federal level, despite numerous studies finding instances of workplace discrimination. Late last year the Equal Employment Opportunity Commission filed suit under the ADA on behalf of an obese woman on the theory that her employer perceived her to be disabled. Undoubtedly the obese workers who have lost out on jobs or been subjected to harassment at work will be watching the case closely.

If you’ve done time.

If you’ve spent time in prison and don’t want that to work against you in the hiring process, you don’t have much recourse on the federal level. With that said, some states have adopted laws limiting employers’ ability to screen applicants based on criminal background, presumably on the theory that an ex-con who can’t find a legitimate job on the outside is more likely to return to a life of crime. Massachusetts, for instance, recently changed its laws to ban employers from asking about applicants’ criminal history before an interview.

“It isn’t a protected class per se, but they didn’t want employers to automatically screen out [people with criminal backgrounds], so they limit what you can ask on an initial application,” says Michele Randazzo, an employment lawyer with the Massachusetts law firm Kopelman and Paige PC. “That’s not to say they can’t ask about it in the interview.”

If you’re litigious.

Other types of legal history carry more protection, at least in theory. While employers may be wary of hiring someone with a history of filing discrimination lawsuits against former employers, discriminating on that basis is indeed illegal; Randazzo points to the EEOC compliance manual, which states that “An individual is protected against retaliation for participation in employment discrimination proceedings even if those proceedings involved a different entity.” As such, any company foolish enough to ask a prospective employee if he or she had previously filed such a lawsuit would expose itself to legal liability if it subsequently decided not to hire the person.

Of course, in the age of Google, finding out whether a would-be employee has a history of litigation may not require asking the employee at all, and Randazzo acknowledges the possibility that “someone who has filed a discrimination complaint against a former employer may have a hard time getting hired by another employer.”

Indeed, such gray areas are a concern even if you belong to one of the protected classes. Take age discrimination, for instance. While officially prohibited by law, companies seeking to cut costs may be less inclined to hire more “experienced” workers who would command a higher salary than someone fresh out of college. And as long as the employer doesn’t give any inkling that age (rather than salary) is the deciding factor, Randazzo says an aging worker would have a tough time proving illegal discrimination has occurred.

—For the best rates on loans, bank accounts and credit cards, enter your ZIP code at BankingMyWay.com.