The Obamacare ruling is very scary. The government cannot order you to engage in commerce, but can tax you if you don't. The reverse is also true. They can't prevent you from engaging in commerce, but can tax you if you do. A scenario.....noone can prevent you from owning firearms because of the 2d Amendment. But they CAN require you to report the number and types of firearms you own so you can pay an "appropriate" tax.