The US authorities' campaign against aggressive tax shelters was dealt a blow last week after a Texas judge ruled that the government exceeded its power by outlawing a shelter known as 'Son of Boss'. In a 28-page judgement released last Thursday, Judge T. John Ward of the US District Court for the Eastern District of Texas wrote that regulations issued by the IRS in 2000 did not apply to taxpayers who used the tax shelter prior to this date. According to Judge Ward, the government's retroactive application of these rules was an "abuse of discretion"./p> The civil case was brought by two Texas lawyers, Harold W. Nix and C. Cary Patterson, who sued the Internal Revenue Service in 2004 after the agency denied deductions resulting from the use of the tax shelter four years previously.