Certain car modifications are allowed in the country where I live. They are not so strict about this. However, they are strict if you want to do major modifications to your engine that would harm the environment or make your car extremely loud. These types of modifications are prohibited and can't be done.
If you want to change tires, raise or lower the chassis, or change out the engine for a larger one, this is possible. Not many people here work on cars so this one makes it a bit more difficult to do any major modification yourself. They would be forced to take their car to a garage and have them do the work for them.