The National Labor Relations Board says you have the right to bellyache about your employer online -- but there are few important limits.

The right of workers to get together and moan about their bosses has been enshrined in U.S. law ever since 1935, when President Roosevelt signed the landmark National Labor Relations Act. The heart of the statute, known as Section 7, guarantees employees the right to organize, collectively bargain, and "engage in other concerted activities" for their "mutual aid and protection." That basically means you've got permission to whine about management at a bar without getting canned.

These days, that right also extends to the (often whiny) free-for-all that is social media. In a series of reports and rulings this year, the National Labor Relations Board clarified that you are indeed entitled to log onto Facebook or Twitter and gripe about your employer without facing retribution. Of course, all rights have their limitations, and this one is no exception, as attorney Philip Gordon explained in an interview with Bloomberg Businessweek this week. Gordon relates the fascinating case of Knauz BMW, the moral of which is this: If you're determined to make fun of your company, keep your lacerating wit focused on stuff involving your actual job.

Here are the facts of the case, as Gordon realtes them: Knauz BMW, a dealership outside Chicago, decided to throw a soiree of sorts for its customers, and management thought it would be fun to roll out a hot dog cart for the party. Its sales team argued -- to no avail -- that an event full of luxury-car owners needed a classier menu, and when the day came, a salesman named Robert Becker snapped some photos of the cart and loaded them onto Facebook "along with snide comments," as Gordon puts it. 

Unfortunately, Becker's snarking didn't stop there. Knauz BMW was part of a chain of family-owned franchises that included a Land Rover dealership across the road. In an unfortunate but sort-of-hilarious sounding incident, a customer's 13-year-old son was allowed into the driver's seat of a Range Rover and proceeded to barrel the vehicle over a bystander's foot and into a pond. Becker once again snapped some photos and loaded them onto Facebook alongside his color commentary. 

Becker was fired, and his case ended up before the NLRB. Here's Gordon's explanation of what came next: 

Becker contended that he'd engaged in protected concerted activity and shouldn't have been fired. The NLRB decided that the post about the hot dogs was protected because it was an outgrowth of an earlier meeting with management. But Knauz argued that they'd fired him after the Range Rover incident, which wasn't protected. It wasn't a joking matter and it involved a customer. The administrative law judge agreed: The termination was lawful.

So got that? If you rain down vitriol over your employer via Facebook because someone didn't take your advice on catering, you're all in the clear. But if you mock the company for stuff that's entirely unrelated to you, your job conditions, or your coworkers', you may be packing up your desk. At least, that's the case for now.

Although the NLRB has stood up for the Internet's kvetchers so far, it's decisions can technically get reversed by a federal appeals court. And now that there's a serious chance the Obama administration's recess appointments to the NLRB could turn out to be unconstitutional, the fate of all its recent decisions is a bit shaky. You've been warned.