NEW DELHI—When Amrita Mishra passed the bar exam, she rushed out to pick up one of the biggest perks of being a lawyer in India: an “Advocate” sticker to slap on the window of her car.

A car’s window sticker, also known as a Monroney label or Monroney sticker, is required for every new car sold in the U.S. The “Monroney” name comes from Senator Monroney from Oklahoma, who ...