Since this discussion is about legal aspects, do you have a citation for legislation or significant court case that defines employment as not being voluntary?
Don't have to. The state regulates the employment contract on a regular basis. Minimum wage, overtime, child labor, OSH, the right to know act, FLSA, EEO, and others.
As to the earlier argument that forcing a property owner violates the 5th Amendment as a taking, I will repeat:
The Takings Clause of the Fifth Amendment, made applicable to the States through the Fourteenth Amendment, provides that private property shall not be taken for public use without just compensation. The Takings Clause does not prohibit the taking of private property, but instead places a condition on the exercise of that power. It is designed not to limit the governmental interference with property rights per se, but rather to secure compensation in the event of otherwise proper interference amounting to a taking.
In addition to outright appropriation of property, the government may effect a taking through a regulation if it is so onerous that its effect is tantamount to a direct appropriation, this is known as "regulatory taking". see Lingle v. Chevron U.S.A., Inc., 544 U.S. 528 (2005).
In Lingle, the Supreme Court provided a framework for addressing regulatory takings. First, a court must determine if the regulation results in one of three types of regulatory takings. These occur: (1) where a regulation requires an owner to suffer a "permanent physical invasion" of the property; or (2) where a regulation completely deprives an owner of "all economically beneficial uses" of the property; or (3) a government demands that a landowner dedicate an easement allowing public access to her property as a condition of obtaining a development permit.
People carrying on your property do not deprive owners of all economically beneficial uses of their property, but do result in an unwelcome physical invasion onto a business owner's property by individuals transporting and storing firearms in their vehicles. It is apparent the invasion onto an employers property is unwelcome if they have corporate policies preventing weapons on property. see Loretto v. Teleprompter Manhattan CATV Corporation, 458 U.S. 419(1982)
In Loretto, the Court distinguished temporary physical "invasions" from permanent physical "occupations." The court ruled that an invasion is temporary, while an occupation is permanent.
A physical occupation, as defined by the Court, is a permanent and exclusive occupation by the government that destroys the owner's right to possession, use, and disposal of the property. see Boise Cascade Corp. v. United States, 296 F.3d 1339, 1353 (Fed. Cir. 2002)
People carrying weapons do not force any permanent "physical structure" on an owner's property. Instead, they force an unwanted physical invasion by third parties engaging in an unwanted activity. The invasion itself is not "permanent" because the individuals engaging in the unwanted activity (carrying guns) do not remain on the property at all times, as would an actual physical structure. Nor does CCW cause a "permanent" invasion with regard to a particular parcel of property, such as the public bike paths at issue in public easement cases. In those cases, even if no person ever chose to ride his bike across a public path, there is nevertheless governmental intrusion because that particular parcel of land is stripped of its right to exclude.
If no individuals choose to engage in the activity of CCW, landowners will not suffer unwanted invasions. It is therefore hard to classify the invasion caused by CCW as permanent for purposes of a takings analysis, thus a person who carries a weapon on your property under the law has not violated any of the three prongs necessary to constitute a taking of property under the 5th Amendment.
Our country was founded by men that regarded private property rights above all else. That is the unique experiment that was called The United States of America.
and where in the founding documents is this written?
