Yesterday, and for much of the past year, I regularly did something that was perfectly legal.
Starting today, if I do the same thing, I am breaking a New York State law.
What is it that I’m doing?
The first correct answer earns a signed copy of SuperFreakonomics or a piece of Freakonomics schwag.
Addendum: The answer and winner are announced here.

You buckled your 7-year old child into a regular seatbelt. As of today, he/she must be in “an appropriate child safety restraint system,” which requires more than the standard car seatbelt and cannot be in the front seat.
See: http://www.nydmv.state.ny.us/broch/c-1.htm
yeah…the booster seat law…I’m glad my kids are all over 8
Your 8 year old child is riding without a booster seat?
You are letting your seven year old text and drive without an appropriate child safety restraint system?
jaywalking?
Holding an illegal lottery!
Your kid isn’t eight and he is riding in your car without a child passenger restraint.
Talking on a cell phone while driving.