This is like seat belts in cars.
First the gov says they need to be in cars, but you do not have to wear them.
Then, you have to wear them, but we will not stop you for not wearing them.
Then, you have to wear them and we will stop you and ticket you if you are not wearing them.
Now, we have roadblocks (checkpoints) to see if you are wearing your seat belt.
Don't let them start.