There is a new bill in Congress that is expected to pass that would allow the government to suspend your travel outside the country if you own taxes to the IRS.
There is no requirement that the tax payer be guilty of or even charged with tax evasion, fraud, or any criminal offense - only that the citizen is alleged to owe the IRS back taxes of $50,000 or more.
Bill in Congress could suspend your passport if you own taxes to the IRS - The Daily Economist