Employment law in the European Union creates a level playing field for rights at work, holiday entitlement, expectations of safety and, importantly, limits to the hours people can be required to work. This matters in a world where it is easy to move jobs from one country to another.
Those limit on hours are quite simple really, but remember how we were told that having a limit of 48 hours (which is quite a lot) it would put small firms out of business? Well of course it didn't. Just as the minimum wage didn't put anyone out of business either.
But these are the aspects of EU law that the Conservatives hate most. They were always happy to have the Single Market, but without the protections to people at work that Labour brought in when it won the 1997 election.
So when you hear them say 'the Maastricht Treaty changed it all' they say they are talking about sovereignty, but they are not. They are talking about the rights created for ordinary people at work. Now they say they will protect those rights, but ask yourself this - if the Conservatives really care about the rights of people at work why have they resisted every serious attempt to improve those rights for the past 150 years.
