... are delimited by the Constitution, including the Bill of Rights.
The interpretation of those "limits" is defined by the Judiciary (that is the various courts and the Supreme Court).
There is no variation in the above documents, whereas there are Great Variations in terms of their interpretation. Which are more or less large depending upon the prevailing sentiment.
In fact, some think interpretation (of the Constitution) is historical in nature and thus passes in waves; changing every thirty of forty years and largely depending upon the nature of the Supreme Court. That is, whether the laws politicians pass by nature are consistent with - or not - the Constitution.
So far, so good - no great evil has been done. But evil is in the eye of the beholder.
And anyone with an "eye" for Social Democracy will say that the US is one of the most inequitable and unfair nations on earth.
Generally because the fruit of one's labor, revenue, are taxed and returned as "government services" is not sufficiently equitable. Meaning what? Meaning that they are not fair and impartial. (More than half of discretionary Federal Budget goes to just the DoD!)
Beyond this general explanation, we delve into the nature of work, how it is compensated and whether that compensation has especially favored one group (workers) over another (producer-owners). How is that measured? In terms of after-tax revenues ...