Alright, so the creation and enforcement of laws begins with community standards. The idea being that laws should limit the amount of friction in interpersonal relations.

This has little to do with actual wording or even about drawing hard lines since the actual enforcement is done at the local level. Historically, the concept of the word of the law (de jure), and actual rules people follow (de facto).

So, the problem you're having is that you're wondering where exactly your personal liberties are unfairly curtailed by the letter of the law, when the reality is that the actual enforcement is up to local authorities - also a reflection of the community they serve.

Now, this example isn't perfect: many elites write laws that unfairly help them or hinder others, and plenty of authorities enforce things that hurt their local populace. But for the most part, these stand. The creation and enforcement of laws has the express intent of causing the least strife amongst its people.

So, where's the line in your burka question? It's whatever your community says is alright.

The onus is on people in a minority to convince others that their differences aren't disruptive to the society around them. This works for better and for worse, and it's the price of living in a democratic society.