Video/DVD certificates

One of the DVDs I borrowed from the library has two certificates on-a UK 12 certificate and an Irish 15 certificate. How come the same program be suitable for 12-15s to view in one country but not another?

Oh and whilst we’re at it, how come things like my Friends videos have 12 certificates? It seems daft that someone can watch the program quite happily on TV but if they wish to rent the video and watch the exact same program, they can’t…

in answer to your first point, that is no different to the laws that allow people of 18 years and over in the UK to drink alcohol, yet their counterparts in the States are not allowed to drink legally until the age of 21. Different countries have differetn laws/standards.