Roxxanne Vigil rushed home from a barbecue one recent Wednesday night to find her back door open and the fugitives she was hiding gone.

Neighbors had called her cell phone, warning that the police were at her house in northwest Denver. The officers had departed by the time Vigil returned, but they had left a notice for her on the front door. The clock was ticking: She had seven days before the fugitives would be executed.

Vigil, 19, consulted her sister and mother. There was only one hope for the family dogs Baby and Chopper: the pit bull underground railroad, an elaborate rescue network that spirits condemned canines off death row.

Denver's on-again, off-again ban on pit bulls has driven some dog lovers to distraction since it was reinstated in May. The ban requires pit bulls found within city limits to be held for a week. They are killed if they are not claimed. A dog is released only if the owner finds someone who lives outside the city to take custody. If the pit bull is found again in town, there is no second chance. The dog will be euthanized.

Some dog lovers have sold their houses and fled the city rather than part from their pets. One man backed out of buying a house and lives out of a camper shell in his pickup with his two pit bulls. Others have stayed in town but lead a clandestine existence, dodging authorities and concealing dogs, dashing across city limits when it is time for a walk.

In the nearly three months since the ban was reinstated, Denver has euthanized more than 290 pit bulls. Baby and Chopper's father, Buck, was caught by Denver Animal Control and put to sleep last month.

The director of the city's animal shelter, Doug Kelly, said the city had little choice but to level the ban.

"When pit bulls bite, they can be very, very serious bites which can end up more often than other breeds in serious bodily injury and death, and that's something that the city just can't ignore," said Kelly, who has received e-mails and letters from around the world tarring him as a "Pit Nazi."

"The rhetoric can get pretty strong," Kelly said.

Pit bull owners say that is because the city is messing with family.

"It's like, 'You can keep one of your children, but this one is too stocky, too broad a jaw,' " said Sonya Dias, a loan officer who helped found the rescue network. As she gained notoriety for fighting the ban, Dias sent her pit bull, Gryffindor, out of town.

Even though the group adopted a staid name -- Breed Awareness Not Discrimination -- it has been tagged the underground railroad. In addition to rescues, the group, which numbers about 300, stages protests and circulates petitions against the ban, and has joined a lawsuit to overturn it.

Denver is not alone in banning pit bulls; cities including Cincinnati, Miami and Lanett, Ala., have outlawed pit bulls.

First bred for fighting in the 17th century, pit bulls come in all colors, stand as tall as 2 feet and weigh as much as 55 pounds. In rare cases, they weigh twice that. With thick necks and huge jaws, pit bulls are known for their strong bites and a refusal to let go. People hearing about a dog attack on a human often assume it is a pit bull. That is a reputation that Denver's pit bull lovers are furiously fighting to change.

They argue that pit bulls, like any dogs, attack only if trained to do so or if neglected by their owners. They note that pit bulls were once known as exemplary companions for children and the infirm -- Helen Keller had one, as did the Little Rascals. They say laws that punish owners for the dogs' bad behavior are more effective than outlawing all pit bulls.

The Vigils say they never saw any killer instinct in Baby or Chopper.

They settled on pit bulls as family dogs after watching a friend's dog play placidly with a baby and the Vigils's young cousins, nieces and nephews. Roxxanne and her sister Robin picked puppies from that dog's litters last summer and winter.

The only problem, they said, was the dogs' need for affection. "They lick you to death," said Augusta Vigil, the sisters' mother. "They never bit anyone."

The new members of the Vigil family arrived just as a truce was declared in Denver's pit bull wars.

The city had banned the dogs in 1989, after a 3-year-old boy was killed and an influential minister was mauled in separate attacks. Animal groups long fought the ban, and in spring 2004 the state Legislature passed a law forbidding Colorado cities from outlawing specific breeds of dogs, which nullified the Denver ban. The city sued to overturn it, but for a year, pit bulls were legal.

Then came the District Court's decision in mid-April: Denver had the right to regulate dogs. The ban would return within 30 days.

The Vigils rearranged their lives to hide Baby and Chopper. Augusta Vigil did a little research. That is how she discovered the pit bull underground. When the police arrived that Wednesday night -- tipped off, the Vigils suspected, by a neighbor who heard Baby and Chopper barking -- Augusta called the underground's Rita Anderson.

An animal rights activist who lives in the famously liberal university town of Boulder, 35 miles northwest of Denver, Anderson is known as the woman who gets dogs off death row. By her count, she has saved more than 30 by signing agreements to take them out of Denver.

City officials welcome her help. "We want them to get pit bulls out of Denver," said Kelly, the animal shelter director.

Anderson's day job, which included a recent campaign against monkey experiments at the University of Colorado, normally absorbs all her time. But when Dias became overwhelmed with calls from pit bull owners, she turned to her activist aunt, Anderson, who agreed to assist the rescue network.

Thirty-six hours after Baby and Chopper were confiscated, Anderson, Dias and the Vigils strode into the squat concrete bunker in southwest Denver that housed the city's animal shelter.

With dogs yelping in the background, Anderson and Augusta Vigil read and signed a sheaf of papers. Dias, a public notary, was there to certify the signatures.

An animal control officer then led the Vigils into the heart of the shelter, where Chopper and Baby were released to their owners. The dogs were implanted with microchips that would allow animal control to identify them as pit bulls that had already been detained. Baby and Chopper could not stay in town anymore. Their next home would be Mariah's Promise, a 43-acre dog refuge underneath Pike's Peak founded by Toni and Mike Phillips, who operate a sheet-metal business in Colorado Springs.

Mariah's Promise sheltered a dozen or so dogs as well as the couple's four cats -- until Denver's pit bull ban was reinstated. Now the property is dotted with spacious, open-air kennels holding more than 80 dogs, half of them pit bulls. The refuge's one requirement is that the dogs be neutered.

Plenty of dog lovers are defying the ban.

A 29-year-old graduate student keeps her pit bull, Jack, inside her house with the blinds drawn. She removed the mailbox from her front porch so the postal carrier would not be tempted to peek in. The student, who did not want her name used for fear of losing Jack, said that when she drives across city limits to take him for a walk, she inevitably passes police cars and prays that her outlaw dog stays down in the back seat. "I don't know how people on the lam do it," she said. "It's stressful."

Rich, who did not want his full name used to avoid being caught, deals with even more stress because of his extreme measures. When the ban was first in place, the 38-year-old sound technician hid his two pit bulls for four years while he lived in a rented house in Denver, sneaking outside the city for their regular walks. After the ban was lifted, he came out in the open. He walked the dogs in the city's parks and was about to buy a house when the city announced it would resume rounding up pit bulls.

Rich backed out of the house deal, losing thousands of dollars. "Anything's better than being stuck in Denver and not being able to have my kids in my house," he said. "I love the city of Denver. I wanted to settle here, and they chased me out."

Rich had nowhere to go; his work was still in the city. So he jammed a mattress and a small propane-powered stove and refrigerator underneath the camper shell on his pickup and became a vagabond. On workdays, he parks in the shade and leaves his pit bulls in the truck with a cooler of ice and the sunroof open. He crosses city limits at night to shower at friends' homes, walk his dogs and sleep with them in the pickup. Meanwhile, he is looking for a house in the suburbs.

In the Vigil household, Robin also was trying to find a new place in the suburbs, so she could live close to Denver with Baby and Chopper. In the meantime, she planned to take the pit bulls to Mariah's Promise.

Then, at the last moment, her grandparents drove to Denver from their mountain home and offered to take the dogs. Baby and Chopper now live in Fairplay, about 85 miles southwest of Denver.

They will stay there for some time. In the past month, two cities near Denver have also proposed pit bull bans. The uncertainty has stalled Robin Vigil's dreams of reuniting with Baby and Chopper. She has halted her apartment search because she does not know what town may outlaw pit bulls next.

An unidentified Denver man rests in his pickup truck with his pit bull. The man said he was about to buy a home when a ban on pit bulls was reinstated.