If you have been keeping track of the patent lawsuits between Apple and Samsung, you may remember that Samsung recently won its case with the U.S. International Trade Commission. The commission ruled that the iPhone 4 and the iPad 2 infringed on Samsung’s patents. So the commission banned the sale of them in the U.S. Then the Obama administration vetoed that decision.

To avoid getting tangled in the menacing jungle that is patent law, let’s start with a simple question. Why veto the commission’s ban on iPhones and iPads if Apple was infringing on Samsung’s patents? The answer: It’s for the public good.

“What the administration is saying is sometimes just let the infringement continue because taking some step might harm the public interest” says  Dennis Crouch, a law professor and the author of the patent blog Patently O.

In this case the public interest is not just about our desire for iPhones and iPads. It’s about standard essential patents. That means patents that cover an essential piece of the technology needed to make a device function.

“The administration also focused on Samsung’s prior statement that it was going to be willing to license its patents in a reasonable way,” Crouch says.

In other words, the administration doesn’t think Samsung lived up to that promise.

The harder question, says NYU law professor Rochelle Dreyfuss, is, “what’s a reasonable rate? Because the patentee says the reasonable rate is a high figure and everyone else in the industry says the reasonable is a low figure. And that’s why there are so many of these cases.”

The latest case will play out today in a federal appeals court. Apple wants the court to ban some of Samsung’s older smartphones. If the court rules in favor of Apple it could force Samsung to change designs for future products. But financially speaking the ban will have little financial effect on Samsung. The smart phones Apple wants banned account for less than one percent of Samsung’s sales.