The city of San Marcos, Texas is taking a second look at its mandatory pet micro-chipping law.
Protestors shot video at a candlelight vigil held this week to oppose the new policy. They say it violates pet owner's rights and also poses a health risk.
Several studies show chip implants can cause malignant tumors in lab rats and mice.
"People are becoming very concerned that the government is becoming more and more intrusive in their lives," microchip expert Katherine Albrecht said. "And when you start talking about the micro-chipping of animals we're talking about a pretty invasive procedure.
"And I think for a lot of people there's a real worry that if we allow the government to say we must microchip our animals then it's just a matter of time before that government says we must microchip our children and even ourselves," she added.
Animal control officers in San Marcos say dog collars often come off and they are trying to avoid euthanizing unidentified pets.
Several large cities in Texas and California have already passed mandatory pet chipping laws.