Social media companies are the global corporate giants of our time. They make vast profits and hold great influence over our governments and institutions. However, the inconvenient truth is that they have only managed to become so powerful and profitable because they help themselves to our personal data. These are mostly US companies – but they extract and exploit vast amounts of data, and with that data economic value, from British citizens.

At a time when many are struggling with the cost of living, it is paradoxical that vast amounts of money are being made by the richest companies in history from the data being provided by the same people. This data often contains extremely intimate personal information, which is then used to influence people’s behaviour.

Despite protections under British law, the social media companies have been allowed to get away with these activities largely unchallenged. They need to be reminded that they are not too big to have to abide by our laws. That is why the news that Tanya O’Carroll, a human rights campaigner from London, has reached a settlement in her landmark case against Facebook’s parent company, Meta, is a most important development.

Four years ago, O’Carroll wrote to Meta stating that she wished to exercise her right under Europe’s general data protection regulation or GDPR to object to the processing of her personal data. The law is clear that the right to object is absolute when it comes to targeted advertising, and people are entitled to exercise the right free of charge.

O’Carroll was worried about the extremely detailed and private information that Facebook was using to target advertisements at her – including matters such as her family relationships, financial interests and political views. This wasn’t information that Tanya had provided to Facebook, but characteristics it had inferred about her based on her activity online.

Now, just days before going to trial, Meta has agreed, for the first time, to stop targeting advertising to a user, based on their personal data.

O’Carroll’s case is certainly a watershed: it suddenly opens up the possibility for millions of people across the UK to follow in her footsteps, and object to the processing of their personal data by Meta. The nonprofit organisation Ekō is running a campaign to help people do just that.

By using their right to object, people could trigger a change in their relationship with tech giants. Instead of continuing to passively be the product that these companies sell to advertisers for vast profit, social media users may now be able to force these companies to rethink the value they offer them. Locking in users and huge, seemingly guaranteed, profits have long created hubris among the social media platforms – and, in recent years, a sharp decline in the quality of the product that they offer.

This could therefore be a significant moment in the short history of social media in our country. It is crucial that our courts and regulators now robustly enforce the law. The Information Commissioner’s Office (ICO) intervened in support of O’Carroll in the run-up to this outcome. Now, if Meta starts to push back, the ICO must enforce the right for others to object.

But the government could still get in the way. The tech giants have considerable influence over politics around the world, and the UK is no different. The government has suggested that it will create a favourable policy environment for these US companies to do what they like with British consumers. The decision to replace the head of the Competition and Markets Authority with a former Amazon boss looks like a step in this direction and this must not happen with the ICO and other regulators. It is also crucial that potential legislative changes under the data (use and access) bill do not undermine the ICO’s independence.

If the law is now properly enforced, O’Carroll winning her right to privacy against one of the wealthiest companies in history represents a significant tip in the balance of power between social media platforms and ordinary people in our country. It is also a reminder of the importance of public interest cases, and how crucial it is that they are adequately funded and thus able to be brought.

For too long Meta has used its size and influence to lobby its way out of accountability. The law exists to protect citizens and uphold their rights. It is high time technology giants were obliged to respect these rights.

• Dominic Grieve was Conservative MP for Beaconsfield from 1997 to 2019, and attorney general from 2010 to 2014