Who among us hasn’t smirked while watching someone else open a package that doesn’t contain nearly as much product as it has room for? This series of images from the johnson banks design consultancy satirizes the mismatch as the essence of “how packaging works.”

But, the amusement stops when the lawsuits start. Pushback against the kinds of partially filled packaging that consumer advocates call deceptive is intensifying—and the pressure isn’t coming only from consumers.

Packaging can be criticized as deceptive for a number of reasons, but the hottest button is “slack fill”: the difference between the actual capacity of a container and the volume of product it holds. Most packages have to allow for a certain amount of slack fill because of machine filling limitations, settling during shipping, package function, and other legitimate factors.

But, any extra space above and beyond this allowance is regarded as “non-functional” slack fill, and the U.S. Food and Drug Administration says it’s misleading in containers that don’t allow consumers to fully view their contents. Because all states have deceptive trade practices laws that can be invoked against non-functional slack fill, differences of opinion about how much of it is and isn’t permissible have plenty of opportunity to escalate into legal wrangles.

California consumers, shielded by their state’s stringent slack-fill regulations, have watched local prosecutors go after Harry & David, Clorox, the maker of Mucinex, and other CPG suppliers for alleged violations. The state’s biggest recent win was against Procter & Gamble’s Olay skin-care products, resulting in a settlement that will require P&G to change the packaging and pay $850,000 in civil penalties and costs.

P&G took a similar hit to its reputation if not to its finances on the other coast last year when a privately-filed class action lawsuit in New York alleged that the some of packages for Old Spice deodorants contained as much as 48% slack fill. (The case was dismissed.) But, P&G is far from being the only maker of name-brand products to absorb punishment for slack-fill violations.

In a settlement with the Orange County, CA, district attorney’s office, Unilever will pay $770,000 in penalties and costs stemming from an investigation that found false bottoms in containers of its Axe hair-care products.

In New York, Perfetti Van Melle USA, the maker of Mentos confections, is fighting a $5 million class-action suit by 100 private citizens who say that Mentos gum containers that can hold 70 pieces contain only 50—a slack-fill void of 29%.

And, for every bar patron who has ever wished that his Slim Jim meat stick had given him just a few more oily bites, the big news is that maker ConAgra is facing a class action suit charging slack-fill deception in boxes of the snacks.

State prosecutors and private litigants don’t have a monopoly on actionable unhappiness over partially filled packaging. In Minnesota, J.R. Watkins Inc. has sued McCormick & Co. over the latter’s packaging of black pepper. Here again, the bone of contention is unseen slack fill.

Watkins, a health and beauty aids manufacturer with a side business in spices, says that McCormick—the nation’s largest spice producer—now packs 25% less pepper into tins with dimensions and price markings that have not changed. This is deceptive despite relabeling for weight, the suit alleges, because it makes shoppers think they are taking home more McCormick pepper than they have actually purchased.

The clamor around perceptions of deception in packaging has grown loud enough to attract the attention of Wal-Mart, which wants to keep itself out of the fray of legal entanglements like those mentioned here. The retailing giant recently ordered its suppliers to double down on their compliance with regulations mandating accuracy in package labeling.

The memo wasn’t specifically about slack-fill practices. But, it did highlight Wal-Mart’s sensitivity to what discrepancies between container and contents can mean to the credibility of sellers of packaged goods.

Packaging printers and converters only create spaces for product manufacturers to fill—they have no say over how much product actually goes in. They mark containers only with the information that brand owners tell them to put there. For them, fortunately, that’s the water’s edge—a safer place to be than the sea of legal controversy that awaits careless or unscrupulous producers of packaged goods.