Graffiti has been governed by one rule ever since it exploded in the Bronx in the 1970s: If you paint over another artist’s work, what comes next must be better than what stood before. In the ephemeral world of graffiti, it was about as close to a law as there was.

Last week, a federal judge, Frederic Block, may have established legal precedent to the unwritten code. Jerry Wolkoff, the developer who owns the building known as 5Pointz in Long Island City, Queens, was fined $6.7 million for painting over the works of 21 graffiti artists. Even though Mr. Wolkoff owned the building that was painted, a jury found that under the Visual Arts Rights Act, the art was protected.

It was an odd and belated sense of validation for the graffiti artists, even though they sensed that Mr. Wolkoff’s legal team underestimated the art form.

“I think going into this, he didn’t realize how organized we were,” said Carlos Game, 47, one of the artists seeking damages. “They forget that these aren’t little kids. These ‘kids’ are 47 years old. They run businesses, they have businesses.”