Ever since the U.S. Constitution was written — boy, it's got to be 20 or 30 years ago, by now — one of the recurring difficulties in American law has been to balance liberty against security. But within the last few years, we finally have figured out the exact value we place on freedom: We are willing to trade it for gum and pizza.

That might have surprised me once. I used to think that test cases for using advanced spy technology on American citizens would involve really bad stuff, such as pillaging or cannibalism or hog stealing — and not, as has turned out to be the case, for marijuana possession, spit wads or illegal watering.

But in the U.S. Supreme Court right now, for example, one marijuana bust could decide whether authorities will use futuristic hardware to look through your walls. After police in Florence, Ore., got a tip that Danny Lee Kyllo was growing pot, they scanned his house with a thermal imaging device that shows indoor heat patterns. The patterns indicated the possible presence of grow lights. So the cops raided the place and found more than 100 marijuana plants.

It's sort of like if Superman used his X-ray vision to check for Grade C misdemeanors. Sure, Kyllo broke the law. But I'd feel better about the techno scan if Kyllo had turned out to be using those lights to dry out shrunken heads.

Meanwhile, in our very own Cherry Hill, the board of education hopes that advanced video technology will make kids shut-the-heck-up on the school buses. The board this week advanced plans to install cameras on all these vehicles, for the express purpose of catching kids doing the same things their parents used to do on those same buses to those same drivers, using much of the same lunch meat.

Constant surveillance by cameras will teach the kids about discipline and make them less surprised when we finally implant that computer chip in their brains.

It would also prepare kids to go to North Carolina, where (according to our friends at the Libertarian Party) some county governments use satellite photos to find unreported improvements that might increase property taxes. Or to Arizona, which employs that technology to find out if farmers are irrigating land without a permit. Or to various highways where police have long talked of setting up cameras to catch drivers speeding, running red lights and, of course, growing 100 marijuana plants.

And why stop there? I once had a roommate who squeezed the toothpaste from the middle of the tube, then placed the cap lightly on the top without screwing it back on, so that when I tried to straighten out the tube, the cap fell off, the paste spilled out ... anyway, we should aim satellite cameras at her.

After all, now that we can enforce the law with scientific totality, shouldn't we do it?

No, in fact not. In this creative society of ours — which once defeated the much more law-abiding Nazis and imperial Japanese — much of our openness and growth depend on letting people get away with a certain amount of illegal but harmless idiocy.

Let me put it this way. Suppose we all were a tribe of orangutans. (I know. It's a stretch.) In any given group of apes, only the dominant male mates with the females. One even might say this is a law — enforceable by having the dominant male jump up and down furiously until he gets distracted and starts eating ticks.

But if the tribe actually obeys this law without question, the entire next generation has the same dad, and the troop gets weaker with inbreeding. What prevents this are a few of the cleverer apes — usually the older ones who survived Iwo Jima and don't give a good gob of spit about anything — who cheat, sneaking fresh, ornery, foul-mouthed DNA into the gene pool.

In the same way, we all stay healthy by committing a few minor, victimless crimes — making fun of the lead ape behind his back, chewing on a few forbidden leaves or paying other apes to pet us.

Besides, if you really want a kid to learn about life, there's nothing more educational than when a bus driver pulls over during a class trip to the planetarium and totally flips out in front of everybody.