This would force governments to re-visit and update old legislation and remove redundant, pointless or out dated legislation with no hassle and without the need to individually repeal every piece of legislation that is no longer relevant.
We could save a lot of time on the subject of repealing legislation if an act was passed which will cause the automatic repeal of all other acts after a fixed duration, maybe 50 years, maybe 100 years, but when that time is exceeded the act should automatically be repealed without further action being required. If there are any pieces of the old acts that are still of use in a modern society then they can be specifically re-introduced and updated by the government of the day before the repeal takes effect.
An example is the banning of markets within 1 day's donkey ride of any market with a royal charter. This centuries old law from the 1200's prevents the setting up of new open markets within 6.7 miles of the existing market as that's judged to be the distance a donkey can walk in a day.
While it may have been sensible in 1210 it has no relevance in 2010.
There are many other laws which may well have been reasonable when first introduced but which are inappropriate now but will probably never be repealed because the time taken to do this for each individual law is prohibitive.