Well there's nothing in the VA Constitution specifically authorizing the Legislature to outlaw prostitution, or beastiality for that matter, and the VA General Assembly does it.
Where do they get their authority to do so?
The State of Va gets its power to write criminal law from its 'police power', hughie.
_____________________________________
Police Powers: Model and Reality
The imaginary model of limited government in the American Federal system deviates from reality. The deflection from truth occurs primarily as a result of the concept of police power.
The model envisions a Federal government possessing only those powers inherent in sovereign nations.
Each state government is assumed to act in a like limited capacity, the limitations flowing both from the National and the particular state constitutions.
All powers not specifically delegated to the state or the Federal government dwell in the individual acting human being. Man is free to do anything not prohibited by state or Federal law, and neither state nor Federal law encroaches upon voluntary action, except in the specific areas reserved in writing to the government in the fundamental charters.
Contrast reality. The government of the United States exercises all powers specifically granted to it by the Constitution and all powers implied from that document.
At the same time, the individual states appear as the Federal government in microcosm with one important distinction:
--- while the Federal government purports, however fallaciously, to be a government of limited powers, the states do not, for they contain the elastic police powers, the great reserve powers of each state.
In legal theory, the states possess all of the ordinary legislative powers exercised by the British Parliament at the time of the American Revolution except as restricted by state and Federal constitutions.
However, no government and no state possesses any "rights".
Only individuals possess rights; any belief that states have rights involves a much too organic view of government.
The state exists not to perpetuate itself in power but to secure the inalienable rights of individuals residing in that territory to life, liberty and property.
It remains to review in cursory fashion the objects to which the police power is often directed: public safety, health, order, morals, and welfare.
In each category lurks the very real danger of the use of police powers to curb creative endeavor beyond the proper scope of state authority.
In the name of public order, the state may circumscribe or wholly proscribe gambling, drunkenness or public meetings; in fact, such repressions affect the free flow of ideas and action whether or not the majority agrees with the value of the action.
In the name of public morals, the government penalizes indecency, adultery, prostitution and "immorality," matters much better left to the decision of adult participants.
In the name of public welfare, the state plunders some and gives to others, a most devastating kind of immorality undeserving of the name of charity.
In each instance where the state exceeds its proper perimeters of preventing force and fraud and providing common justice, the application of police powers destroys human liberty and nurtures tyranny.
Excerpts from:
Police Power: Sovereignty's Sledgehammer
Address:http://www.janda.org/b20/Lectures/Week%203/PolicePower.htm
Superior firepower and teh complacency of the People. Just because they do it, does not make it right, legal, ethical or just.