Straight-pipe exhaust: UK vs US vs Norway

Removing the silencer is an offence on its own before you reach the separate question of what happened to the catalytic converter, and all three markets say so. The UK and US both frame it as a requirement to keep an effective silencer, with the UK adding that the exhaust must not have been altered to exceed its type-approved noise level. Norway states the principle that the other two leave implicit and that matters most today: silencing cannot be removable or defeatable while driving. That single clause catches remote-operated valve systems used to run quiet past a camera and loud everywhere else, which is a growing category of product and one that a straightforward noise-limit rule struggles to reach.