The moves in Sunderland and Manchester have dramatically brought to a head the six-month stand-off whereby councils have been reluctant to prosecute the estimated 38,000 traders who refuse to accept the laws which came into effect on 1 January, making it a criminal offence to sell goods in pounds and ounces.
At a Sunderland market officers called in police support their seizure of three non-metric weighing machines from a fruit and vegetable stall run by Steven Thoburn.
A legal letter sent to the head of Sunderland tradings standards from the office of Jeffrey Titford MEP, leader of the UK Independence Party, claims the officers were in several respects acting in breach of the Weights and Measures Act 1985 - not least in that under section 79 officers must apply for a warrant before seizing scales.
Until now officers have been reluctant to prosecute any of the traders who continue to sell in pounds and ounces because an array of barristers consulted by the British Weights and Measures Association and the UK Independence Party unanimously advise that the metrication regulations introduced by the Conservative government in 1994 were illegal.
These were intended to overrule the Tories' own Weights and Measures Act 1985, authorising use of imperial measures. But the lawyers argue that a mere statutory instrument, secondary legislation, cannot in law be used to amend primary legislation, an Act of Parliament.
When Mr Titford's office put various legal points to Sunderland's chief executive, Bob Bowman came back with a promise that no more scales would be seized until the council's policy had been 'thoroughly reviewed'.
He promised to give 'due consideration' to Mr Thorburn's requests to have his scales returned and repayment in full of the£1,304 he had spent on buying 'imperial/metric' replacements.