A mural in Arlington County of smiling, playful cartoon dogs, complete with paw prints and doggie bones, is now the subject of a federal lawsuit.

Kim Houghton, owner of a dog day care and grooming business in Shirlington, filed a lawsuit in U.S. District Court on Thursday arguing that Arlington County violated her First Amendment rights when it ordered her to cover the mural with giant tarps because, the county said, the mural could be construed as a sign benefiting her business even though her company's name isn't anywhere on the painting.

At the center of the controversy is the nearly 1,000-square-foot mural of cartoon dogs that Houghton commissioned on a wall outside her store, Wag More Dogs, and facing a local dog park.

As a sign, the mural easily exceeds the county's 60-square-foot limit on sign size. But the real problem, Arlington officials said, is that because the mural includes dogs, it qualifies as a promotion of her business. Had the mural been a painting of something unrelated to her business -- flowers, dragons or ponies, for example -- it would be fine.

Houghton said she paid for the mural, which was painted months before her store opened, as a way to give back to the community by beautifying the dog park.

But when Houghton applied to the county to open her business, the county withheld her building permit until she agreed to a temporary compromise, covering the mural with several blue tarps.

A local civil liberties law firm, the Institute for Justice, is representing Houghton. Attorney Robert Frommer said the case is a clear violation her First Amendment rights, and filed for a preliminary injunction that would allow Houghton to uncover the mural while the case is making its way through the courts.

"The First Amendment really doesn't give government bureaucrats the right to play art critic," Frommer said. "We wanted to protect both Kim's right to speak and her right to earn an honest living."

Frommer said the county gave Houghton three options: paint over the mural, add the words "Welcome to Shirlington Park's Community Canine Area" or have her business shut down and face thousands of dollars in fines.

Arlington County zoning administrator Melinda Artman said the county doesn't regulate content, but does regulate signs for size, placement and number.

"Arlington County very much supports its small businesses, especially the small businesses that comply with the law," Artman said. "Those few that happen to inadvertently run afoul of the zoning ordinance pretty cheerfully, once they're made aware of it, rectify the problem."