I have not looked much into the Texas constitutional carry law passed recently (I’m licensed and nothing has really changed). However I do have one question.
Is it illegal to carry a gun without a license into a business that has a sign that says “Must have a license to possess firearm”?
The recent open carry law did not change penal code 30.05 and penalty for not following posted signs meeting 30.06 and 30.07 requirement. It’s still a Class A misdemeanor.
It also did not include the “savings clause” originally proposed. So even if you left immediately after you were told, you will still be charged.
No, it is not illegal. The business must have properly displayed signs (30.06-30.07) as defined by the state at all public entrances. (Technically if you find a door that does not have the sign you have a defendable argument.) Also, the universal NO sign over a handgun sign does not meet the state requirements and means nothing legally.
You are correct based on what I remember from my LTC class. What i am still wondering is how property owners rights are allowed to override the 2A Constitutional Right to bear arms. Yes, there are well established property rights and they are backed by case law, but they are not spelled out in the Constitution as are the 2A rights. If you have a God given right to life, liberty and the pursuit of happiness and the God given right to bear arms per the 2A, why are property owners allowed to take that right away? It seems that their ‘property rights’ are ‘lesser rights’ than the specific Constitutional right to bear arms.
Hey, @Scoutbob, here’s what is on the USCCA Reciprocity Map today (9/13/21)
Please be sure to check the Reciprocity Map for updates as there may be changes since the above graphic was posted.
It looks like they actually made the laws easier to ban firearms at businesses from what I’ve read. 
. I’m not sure if I like this actually worked out. I’ll have to read more on it.
Updat: NVM some of the sights that sum up the gun laws are vague. These laws can be quite confusing sometimes 
and it’s scary they can change so fast.
I have been reading in our State Laws of FLORIDA, that the signs that are posted like at a restaurant here
in Florida that even though it is not allowed to carry a firearm in that business, the police do not enforce
that posted sign. Still, you can stay quiet and tell no one of your carry status, or take your chances.
UNWISE !
Please use common sense, please. I have to own a CCW or permit to carry, but training and practicing good stewardship and being better in our responsibilities’ to carry a firearm is much better. If you do
not fully know things like this, ask a police officer, I love that one, no joke. You can be asked to leave the business, please do; their lose, not yours.
On our school grounds’ and buildings’, are illegal to have in your car or on person, a firearm. and Federal Buildings and Police Stations are illegal as well. That can get rough on anyone’s mind and life.
Understood @William_H I am not familiar with the laws in your state so I don’t have a basis on which to provide input.
But here in Texas, I make a personal choice and tell my students that it is their personal choice whether they wish to carry in an establishment that has a LEGAL sign posted for no OC or CC. Unwise, not necessarily. As an example…
Envision that you are in your car sitting first inline at a red light with your entire family, wife, kids and maybe granny in the car, There is NO cross traffic going through the intersection. You look in the review mirror and see a giant OVERSIZED LOAD banner on the front grill of a semi barreling at you who clearly won’t be able to stop. I would choose in this case, as a wise decision, to break the law and go through the red light to protect my family.
Yes, this is a situation of immediate eminent danger but, you’ll generally never know when you’ll be involved in a DCI so always being prepared would be the wise choice.
With this said, Texas law, it’s not a serious offense if the sign is posted and you carry in that establishment. Regardless of the risk I DO NOT carry in a post office, nor a US Government restricted area, this WOULD be a serious offense.
I hope this helps extend the conversation. 
Thank you very much for you information. Everyone in the USA have been focused on legal issues,
government, and political problems. I am learning to stay out of places that I have no purpose to be in
or to do business with. Your right in your message and it is a challenge to stay focused on, and I have
learned to do my best to follow the rules and laws, to build confidence, to seek and ask questions
if needed. This is not done in legalistically, but in a controlled, but in a relaxed way, and I enjoy joking
with people anywhere I go, respectful and kind to others. Life has changed !
Situational Awareness, there something for everyone ! I use to live in a dull world of what I’m I going
to do today, not any more. I have had people stuck in a cell phone and not aware to the outside world
and walk straight into me, I let them do so with out a word spoken. Using our common sense, our
newly trained minds, intuitively using those things that we must have, maybe stay home with the house full of children and wife. Your the best !
I appreciate in information above and you helped with the valuable things and those crazy little things
that no one pays attention to. Thank you.