When a neighbor known as a liberal Democrat puts a beat-down on a prominent Republican senator, leaving him with lung contusions and five broken ribs, it’s natural to assume political differences must be the cause.

But the leading theory for why retired anesthesiologist Rene Boucher pounded his next door neighbor, Kentucky Sen. Rand Paul, has nothing to do with Obamacare, tax reform or identity politics. Boucher’s lawyer called it “a very regrettable dispute between two neighbors over a matter that most people would regard as trivial.” Reports from in-the-know locals say that means lawn care.

The libertarian-leaning Paul, son of populist-libertarian icon Ron Paul, doesn’t think much of his gated community’s rules and regulations. He “was probably the hardest person to encourage to follow the [homeowners association rules] of anyone out here, because he has a strong belief in property rights,” Jim Skaggs, the community’s developer and a former leader of the county Republican Party, told the Louisville Courier-Journal. Paul originally fought with the association over his house plans.

“He wanted to actually own the property rights and build any kind of house he wanted,” said Skaggs. “He didn’t end up doing that, but it was a struggle.”

Paul grows pumpkins and maintains a compost heap, activities that might go over well in an Oregon tiny-house community but apparently aren’t to the liking of his upscale neighbors in Kentucky. He and Boucher also have a history of disputes over tree trimming and lawn clippings.

“They just both had strong opinions, and a little different ones about what property rights mean,” Skaggs told The New York Times.

Seemingly trivial dispute over lawn care in fact go to deep questions about the nature of a free and pluralistic society. People are different. Do you accept that people are genuinely different and seek institutions that mitigate conflict? Or do you make your personal views absolute?

When it comes to their neighborhoods, some people value the visual harmony of communities with strict aesthetic rules and are willing to pay extra to get it. Others find such homogeneity boring and oppressive. They prefer the self-expression allowed by more laissez-faire regimes.

Property rights, properly understood, allow both alternatives. They let the real-estate market offer neighborhoods with strict rules about paint colors, approved tree species and closed garage doors; neighborhoods with only minimal standards about house setbacks and massing; and neighborhoods without even those rules.

If Skaggs is accurately representing the senator’s views (not to mention the cause of the dispute), Paul has a highly selective idea of property rights. His get-out-of-my-face version of libertarianism doesn’t seem to respect the crucially important freedom to make, and responsibility to respect, contracts.

Your property rights don’t give you the freedom to violate your homeowners association contract specifying how to maintain your lawn any more than my free-expression rights give me the freedom to violate the Bloomberg contract saying I can’t write for The Wall Street Journal. If you can’t live with the restrictions, you don’t sign the contract. And if your neighbor isn’t sticking to the rules, you don’t go after him with your fists. You take it up with the homeowners association — that most local version of politics.