Google has begun removing search results in response to takedown requests from European citizens.
The court ruled that an individual could demand that "irrelevant or outdated" information be deleted from results and that Europeans could seek redress from the courts if firms such as Google fail to respond.
Google is likely to be the company most affected by the ruling because it is the dominant search engine in Europe with 93% of the market, according to StatCounter global statistics.
By comparison, Microsoft’s Bing has only 2.4% of the European search market, and Yahoo has 1.7%.
The landmark ruling forced Google to introduce an online application form after it was inundated with more than 41,000 requests within four days of the ruling, reports The Telegraph.
"This week we're starting to take action on removals requests that we've received," a Google spokesman said.
“This is a new process for us. Each request has to be assessed individually and we are working as quickly as possible to get through the queue."
Read more on EU data protection reform
Google would not say how many individuals' search histories have been changed, or how many web pages have been affected.
Google searches in Europe that involve people’s names include the notice: "Some results may have been removed under data protection law in Europe", and a link to a page explaining the ECJ’s ruling.
However, searches made on US-based Google.com do not include the same warning because the ECJ ruling applies only in Europe, reports The Guardian.
Shortly after the ruling, Google executive chairman Eric Schmidt told the firm’s annual shareholder meeting that the case was a collision between a right to be forgotten and a right to know.
“From Google's perspective, that's a balance," he said. "Google believes – having looked at the decision, which is binding – that the balance that was struck was wrong."
But outgoing European Commission vice-president Viviane Reding said the ruling confirmed the need to bring data protection rules up to date.
"This is exactly what the data protection reform is about – making sure that those who do business in Europe respect European laws, and empowering citizens to take the necessary actions to manage their data,” she said in a posting on her Facebook page.