The Justice Department this week moved on several fronts against tax evasion and the promotion of evasion schemes. Such moves had become so rare in recent years that promoters boasted about not paying taxes and won clients with claims that the government's not coming after them proved that taxes are voluntary. The most significant development came in Las Vegas, where an eight-year prison sentence was imposed on Max C. Tanner, 55, a former Internal Revenue Service lawyer who evaded $2 million in taxes on profits from a stock swindle. Mr. Tanner, who was taken directly to prison, was also fined...