When it comes to illegal immigration, even some liberals understand the danger.

Best-selling novelist Richard North Patterson is the very photograph of modern liberalism. “He lives in San Francisco and on Martha’s Vineyard,” the book jacket says (now that’s a commute), “with his partner, Dr. Nancy Clair.” He’s also a former trial lawyer and chairs the liberal pressure group Common Cause. So when he speaks, we hear the voice of the modern American left.

In his latest novel, “Exile,” Patterson weaves a tale of a Palestinian terrorist bombing on American soil. How does the author get the terrorists into the U.S. undetected? Simple. They jet to Mexico, relax for a few days on the beach, then walk across the border into Texas. “Crossing would be no problem,” Patterson writes. After all, “thousands did it every day.”

But Patterson’s book, intentionally or not, also shows that border enforcement works. The terrorists considered crossing in western Mexico. But “self-appointed American vigilantes had begun spending their idle hours patrolling the borders of Arizona and New Mexico,” Patterson writes. The terrorists didn’t want to be “caught by some white people’s hunt for brown invaders they could not tell from Arabs.”

And with those words from a liberal novelist in mind, let’s turn to the Senate’s immigration “reform” bill.

Last week, the bill seemed dead when senators couldn’t agree to end debate and actually vote on it. Luckily for voters, the Senate had other important business to move on to: debating whether to vote that it had “no confidence” in Attorney General Alberto Gonzalez (although in the end, lawmakers couldn’t manage to vote on that, either).

But the immigration bill’s not dead. “I believe we can get it done,” President Bush announced. “I’ll see you at the bill signing.” Let’s hope not.

Senators who are pressing for a reform bill are making a fundamental mistake, one that’s highlighted by Patterson’s fiction. We don’t need a new immigration law. We need to start enforcing the immigration laws we have.

For starters, let’s complete the border fence.

Just last year Bush signed the Secure Fences Act of 2006. We need to finish building that fence, make sure it’s patrolled and give it time to work. And our brief experience with fences shows that they do work. Last year an observer wrote to tell me that his group (probably the “vigilantes” Patterson wrote disparagingly about) had “shut down approximately five miles (2 percent) of the California border. It obviously can be done.” They did it by building fences and then, along with federal agents, patrolling the border. Continued...