Christmas is coming. You and your friend are in Dublin, wandering down Grafton Street, laden with shopping. You're young, you're happy and above all you look Christmassy - so much so that a newspaper photographer snaps your picture.

The following day, there you are in all your glory on the front page of a national newspaper, with a caption that goes something like "Nineteen shopping days to Christmas". If you're lucky, you'll know the picture was taken, though maybe you won't. If you like the exposure and you're happy for your mammy to know where you were, great. If you don't, tough. The truth is that in many situations you don't own your image.

The photographer owns the copyright and if he or she works for a newspaper the copyright usually transfers to the paper. Out of courtesy, most photographers will ask your permission - but they don't have to. If you really hated the picture, you could get in touch with the newspaper and ask them to delete it from their archive of photos so that it is never used again and most will readily oblige. Other than that, there's nothing really you can do except maybe grumble that your privacy has been invaded.

The situation would be very different if that same picture was used in the same paper to illustrate a feature on shopping addiction. You and your friend could try suing the paper for defamation, claiming that the publication had suggested that you are shopping addicts.

Alternatively, if the picture was used by a shop in its advertising campaign, you could, under the code of the Advertising Standards Authority of Ireland, have the campaign pulled if you hadn't expressly given the company written permission to use the photograph.

The photographer who takes the picture owns the rights to use it. Aside from defamation issues, those rights are limited under the Copyright Act 2000. This protects people who commission photographs such as wedding photos or family photos. The photographer cannot reproduce them without the sitter's permission.

The broadcast media are much more attuned to issues concerning the ownership of images. If you are interviewed for a television programme, you'll quickly be approached by a clipboard-wielding broadcast assistant whose job it is to get you to sign a "model release form" (you don't have to be a model). This is usually a fairly all-encompassing document that allows the production company to use the footage pretty much how they please.

Professional actors and models would immediately point the clipboard in the direction of their agents, but the novelty value of the whole experience usually prompts amateurs to sign on the dotted line with - it must be said - few negative repercussions.

However TV works in much the same way as print when it comes to impromptu shots, such as the aforementioned Grafton Street shopping trip.

A regular feature on news bulletins is a video of a busy street, which is usually used as a backdrop to a report on some aspect of the economy. Permission does not have to be sought from any of those shoppers and too bad if being seen in the street by the nation on the nine o'clock news causes you any problems. If, for example, you should have been in school and the video revealed you weren't, the broadcaster would be able to defend itself by saying that it didn't intend you any harm.

Your privacy is protected in the first instance by the Constitution and secondly by the European Human Rights Convention. If you feel that your privacy had been breached, you could of course take a case, but as one solicitor commented: "We don't get the sort of privacy cases here that they get in Britain." Certainly people sue all the time for defamation, but not on the grounds that their privacy was breached.

Celebrity-watchers will know that the right to privacy has become a hot issue in Britain, with Naomi Campbell, Catherine Zeta Jones and Michael Douglas and DJ Sarah Cox seeking to protect their right to privacy under that country's Human Rights Act.

People in the public eye don't have it easy when it comes to defending their privacy because celebrities exist only because they are willing to be very public. The debate now centres on whether a person has the right to turn their privacy on and off like a tap.

Naomi Campbell is suing the Daily Mirror newspaper over pictures they published of her apparently leaving a drug-counselling centre and Sarah Cox is suing the Sunday People over long-lens photographs taken of her while she was naked on a beach during her honeymoon.

The argument goes that as neither of these women are exactly shy about being photographed when it is beneficial to their careers and are both tabloid regulars, they're fair game. The counter argument suggests that everyone, even those with the most public profiles, have the right to private moments.

The outcome of both cases, which will be heard in the New Year, will have repercussions for the legion of British paparazzi who earn their living by photographing celebrities - sometimes, as they point out, with their permission, other times very definitely without it.

Under the European Human Rights Convention, "everyone has the right to respect for his private and family life, his home and his correspondence".

The Michael Douglas and Catherine Zeta Jones case is slightly different. They famously sold the photo rights to their wedding for £1million to OK! magazine. Security was tight, but somehow a photographer from rival celebrity publication Hello! sneaked a couple of snaps of the happy couple.

A swift court action followed, but the judge ruled that Hello! could publish the photos.