Crossing the border with your dog? The U.S. just changed the rules.

Starting this week, dog owners will have to jump through a lot more hoops to bring their pets into the United States, including those crossing the border from Mexico.

Under new U.S. Centers for Disease Control and Prevention rules, which went into effect Thursday, dogs coming to the U.S. from Mexico and Canada must appear healthy upon arrival, be at least 6 months old, have a microchip that can be detected with a universal scanner, and be accompanied by an import form.

The news has caused some confusion on both sides of the California-Mexico border and created a scramble among many dog owners to quickly get their pets microchipped — an uncommon practice south of the border.

“CDC’s importation requirements apply to all dogs, including dogs that leave the country for short trips, such as to visit family or friends, or to receive veterinary care,” a CDC spokesperson said.

Since the requirements are largely designed to prevent the reintroduction of dog rabies, the rules travelers have to follow will depend on where the animal has been in the last six months. Dogs from a country considered to be rabies-free or low-risk, such as Mexico or Canada, have fewer requirements than dogs from high-risk countries. The list of high-risk countries can be found on the CDC website and includes several Latin American, Asian, African and Middle Eastern regions.