It is usually done by Statutory Instrument so a Minister or more likely Civil servant will modify/change an existing law without recourse to Parliament to bring things in line with current economic or social policy requirements. An excellent example is the recent idiotic change to the UK building regulations mandating that since people are now taller this has somehow changed their center of gravity. Accordingly all new house built must feature bars on the downstairs windows to stop people from fall out and injuring themselves. I jest not see the below link Housebuilders' fury over new rules to put bars on first floor windows - https://www.dailymail.co.uk/news/article-11238393/Housebuilders-fury-new-rules-bars-floor-windows-stop-tall-Britons-falling.html