Did you listen to POTUS Trump’s weekly address yet? He’s slamming CAL for violating the citizen’s constitutional rights with open borders and so on. So that is a state government being constrained by the Constitution.
But what about in the pre-civil rights days with whites only fountains and seating? That was decided to be unconstitutional; violated by private businesses. So it seems that definitely a private entity can violate citizens’ constitutional rights as well.
Have you heard of the land mark case where Christian Bakers were found guilty in violation of a not baking a gay wedding cake?
The Christian Bakery refused to make the cake on the grounds that it violated their religious beliefs. They lost.
For the record, the Bakery did provide other Bakers that said they would be happy to do it, but the gay couple sued the Christian Baker even though they had multiple other bakeries in the city that could gone to.
The Christian Baker lost in court.
Southern states knowingly violated the 14th by passing JimCrowe laws. Businesses, having helped enact them, happily went along with them. Civil rights actions and the resultant 17th(?) Amendment took care of that.
Here’s a better look at the question: how is it a business can deny you your 2nd amendment rights?