FIFA and its European counterpart UEFA argued that the two countries had interfered with their property rights by restricting the broadcast of both competitions to free-to-air TV channels, preventing pay TV companies from bidding to screen them.
TV broadcasting rights for the finals of the major tournaments, each held every four years, account for a significant source of revenues for FIFA and UEFA.
In club football, for example, the English Premier League has became the most richest domestic competition in the world game thanks to live TV deals with BSkyB and other pay TV companies.
FIFA and UEFA appealed to the Luxembourg-based EU Court of Justice (ECJ) after the General Court, Europe's second-highest, last year threw out their challenge to a European Commission ruling backing the British and Belgian decisions.
ECJ Advocate General Niilo Jaaskinen agreed with the General Court.
"If those competitions are considered by member states to be events of major importance for their society, those member states may, in order to ensure broad public access, require that they be broadcast on free-to-air television," he said in a non-binding opinion.
The ECJ will rule on the case in the coming months. While the advocate general's opinion does not tie the judges hands, they follow advisers' recommendations in the majority of cases.
FIFA organises the World Cup finals and UEFA the Euro finals. Media rights for the Euro 2012 tournament, held earlier this year in Poland and Ukraine, were expected to generate revenues of 840 million euros, according to figures from UEFA.
Britain ensures that a number of major sports events including the Olympics remain on free-to-air broadcasters like the publicly-funded BBC.