This week, Google is getting its day in the EU court.

Google's lawyers will spend the next three days in the EU Court of Justice in Luxembourg trying to convince EU judges to overturn a $2.6 billion fine imposed by the European Commission.

Lawyers from Alphabet, Google's parent company, will present their arguments against the Commission's decision to fine the company for abusing its dominant position in the search engine sector.

In June 2017, Margrethe Vestager, the EU's antitrust chief, found that Google had abused its dominant position in the online search market by favoring results that linked to its Google Shopping site. She fined the company $2.6 billion

The five judges hearing the case this week will decide whether they agree with Vestager's analysis. Their ruling on whether to uphold the fine is seen as a crucial test of Vestager's approach to regulating big tech in markets where it dominates.

"The principles the Commission laid down in [the] shopping [case] are foundational for its work in relation to the tech sector," said Alec Burnside, an antitrust partner at Dechert in Brussels.

The fine on Google for anticompetitive behavior in the shopping sector was the first in a series of three areas where the Commission investigated the company and found abuses. The Commission has imposed nearly $9 billion in fines over the past few years.

The two others were into its Android operating system and online search results in the advertising sector. Vestager fined Google $4.73 billion over Android and $1.7 billion for ad search. The Commission has fined the company nearly $9 billion for various market abuses.

The hearing will last three days, during which time five judges will listen to arguments from a group of Google lawyers and a lawyer for the Commission.

"We're appealing the European Commission's 2017 Google Shopping decision because it is wrong on the law, the facts, and the economics," Google said in a statement. "Shopping ads have always helped people find the products they are looking for quickly and easily, and helped merchants to reach potential customers. We look forward to making our case in court and demonstrating that we have improved quality and increased choice for consumers."

Google's rivals had complained that the search engine was exploiting its market share by promoting search results that linked to its Google Shopping site.

Back in 2015, Vestager's predecessor, Joaquin Almunia, wanted to settle with the company by accepting an offer from Google to address the complaints by modifying its behavior.

Other members of the Commission, however, argued that Google's concessions were inadequate to change the offer to consumers and refused to endorse Almunia's recommendation.

Vestager then fined the company after an investigation into allegations of anti-competitive behavior in the market for online shopping, operating systems, and online advertising.