Roald Dahl wrote children’s stories. Two of them—“James and the Giant Peach” and “Charlie and Chocolate Factory”—were made into big-budget Hollywood movies.

Another British writer, Ian Fleming, also penned children’s books. His “Chitty-Chitty-Bang-Bang” made it to the silver screen as well.

But during World War II, both writers exercised another talent. They were British spies. And their target was Washington, D.C. Perhaps it's no surprise, then, that Fleming's most enduring legacy is creating the character James Bond.

At the outbreak of the Second World War, the two countries that spied on America most were also America's most critical allies: Great Britain and Russia. The German and Japanese spy networks in the U.S. just didn't compare.

Britain and Russia didn't invent spying on friends. It's a very old practice that still has a place in the modern world.

Today, revelations from Edward Snowden's leaks offer everyday Americans a glimpse into the shadowy world of American covert operations.

But a glimpse is not a full view. And like any story that doesn’t give the full picture, coverage of Snowden’s more sensational revelations—like eavesdropping on Angela Merkel’s phone calls—has raised more questions than it has answered.

The notion that spying on friends is off-limits made no sense in the World War II era, and makes no more sense in today’s even more complex world. But the espionage game must be played by the same rules—whether it is aimed at friend or foe.

Rule #1: It has to be done for a legitimate national security purpose. The U.S. intelligence community—like the U.S. armed forces—exists for only one reason: to provide for the common defense. It shouldn’t be doing anything that doesn’t serve that core mission.

Rule #2: Any spying must be efficacious. There must be a reasonable expectation that the benefits of the operation will outweigh the costs and risks.

Rule #3. The U.S. Constitution never takes a holiday. Any espionage that runs contrary to U.S. law is beyond bounds. Period.

Rule #4: The programs must be well-run. Incidents like Snowden and Manning walking away with hard-drives filled with secrets are simply inexcusable.

So, too, is stockpiling a whole bunch of information in one place—making it a one-stop-shopping bonanza for Chinese hackers. The government must appropriately safeguard and handle the intelligence it gathers.

Rule #5: The administration, the Congress and the courts all have oversight responsibilities here. They must fulfill their responsibilities with diligence and dispassionate judgment.

And now that we know the rules … here’s why sometimes it’s important to spy on friends.

For starters, it’s good to find out how much they are spying on us and what they are learning. This “two-way street” aspect of espionage was recently glimpsed when the Brazilian government — in the midst of complaining about U.S. spying on Brazil—incidentally acknowledged that the Brazilian Intelligence Agency spies on U.S. officials.

Another legitimate reason for spying on friends: counterintelligence. All friendly nations share intelligence.

And sometimes people working for an unfriendly country steal the intelligence from the friend you’ve shared it with. To find and stop the leak, it may be necessary to spy on each other.

Spying, even on friends, isn’t inherently evil. But stupid, slipshod management of spying is a huge problem.

So is inadequate outside oversight of intelligence programs. Lackluster national leadership that can neither defend nor adequately supervise the intelligence community is a disgrace.

Congressional members that don’t go to briefings, do their homework, or ask the tough questions are derelict.

Washington often has problems acting intelligently. But it has a responsibility to do intelligence well. And it needs to get working on that NOW.

- James Jay Carafano, a Washington Examiner columnist, is vice president for defense and foreign policy studies at the Heritage Foundation.