The strange case of Edward and Elaine Brown

A pair of cranks in America, Edward and Elaine Brown, have been convicted and sentenced to prison for tax evasion, but they are refusing to surrender to law officials and have holed up inside their home. It seems pointless to me that officials have cut them off from the outside world, by denying them electric power and communications etc, and yet allow armed supporters to take them food and drink supplies which only prolongs the siege. Given that the couple own a 110 acre plot, why doesn't the authorities simply take some of their land to cover the cost of the debt?