By Pete Williams, NBC News justice correspondent

In his new book about how judges should decide difficult legal issues, Supreme Court Justice Antonin Scalia says many go about it the wrong way.

"You will see recited in opinions all the way back that the object of interpretation is to determine the intent of the drafter.  I don't believe that.  We're not governed by the drafter's intent. We're governed by laws," he told NBC News in an interview at the court.

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In the book, Reading Law: The Interpretation of Legal Texts, Scalia and co-author Bryan Garner explain that a textualist, like Scalia, is someone who believes that the Constitution and laws must be read on the basis of the fairest meaning of the text.

"Judges should not be using such extrinsic factors as, ‘What is the general purpose of the statute?’ Or ‘What did the Senate committee say when the statute was enacted?’" he said.

But he rejects the notion that such an approach will tend to produce a conservative outcome.

"I ought to be the pinup of the criminal defense bar, because I've written some opinions vindicating the right to trial by jury and the right to confront witnesses.  I'm a law-and-order conservative socially. I wouldn't come out that way if I were king. But that's not my job," he said.

Asked if his views on textualism have influenced his Supreme Court colleagues, he replied, "If so, they've hidden it very well.  All my colleagues had their basic judicial philosophy fixed long before they met me."

Some liberal members of the court have advocated a broader view, notably Stephen Breyer, arguing that judges should pay attention to a provision's purpose when the language is not clear.  "Over-emphasis on text can lead courts astray, divorcing law from life," Breyer has written.

Scalia says the passion in his opinions, especially in his dissents, reflect his view that "there's no sin in caring passionately about doing the right thing.  I care very much about changes to the Constitution that are simply not justified."

But, he says, some people wrongly believe strong words cause hard feelings on the bench.

"I don't translate the hostility to bad decisions into hostility towards the people who are expounding those ideas. And if you cannot do the one without the other, you ought to look for another job.  It's a very unhappy place if you're personally antagonistic to the people whom you disagree with."

As for his future, Justice Scalia, at age 76 the court's longest-serving member, says he intends to remain "as long as I think I'm doing it well."

“I’m very much enjoying what I do.  This is a wonderful job. I like thinking about the law. I like figuring the right answer to legal programs.  And it’s sort of the top of the heap for a lawyer who has those interests.”