I have not been asked to leave anywhere, yet, but here's my plan.
If asked to leave, my first question is going to be: "Are you a 'Person in charge'? Because I am only required to leave by Oregon State Trespassing Law if a 'Person in charge' asks me to leave."
If they do not claim to be a "person in charge," I'll demand to speak to the store Manager or Owner.
If they say yes, or further insist I leave, I will take out my voice recorder (cell phone) andstart recording. I will inform them they are being audio recorded, and tell them to state their name, their position, the request to leave the business, and why they are telling me to leave. I will tell themthat they had better be damn sure they are abiding by their company policy by ordering a paying customer to leave, because this recording will be given to the owner/district manager/president of the company.
If it IS the owner (small business), I will inform them that their business will be added to a national "do not patronize" list, the recording will be posted on the internet, and let's see how they like losing paying customers in this tough economy due to their narrow minded descrimination.
How close I'm going to be able to stick to my plan, I'm not sure. I'll have to see what happens when it happens. If I can spot trouble coming ahead of time, I'll start my recorder before the confrontation starts and notify them they are being recorded as soon as possible.
Yes, I've been nervous OCing, when I first started, and when I OC after not carrying for awhile. After a bit, it gets more comfortable.