Cherie Blair, the wife of former British Prime Minister Tony Blair, is taking on a big legal challenge. She’s representing Mikhail Fridman, a wealthy Russian businessman, in a lawsuit against Luxembourg. This case is all about Fridman’s assets that were frozen because of European Union (EU) sanctions. Last month we informed you about another such case where UniCredit and Raiffeisenbank have taken the Central Bankers to court over Russia sanctions.

Mikhail Fridman, who founded Alfa Group, one of Russia’s biggest private investment companies, is fighting back after Luxembourg froze his assets. He’s suing Luxembourg for nearly $16 billion, claiming that the sanctions against him were unfair and have caused him serious financial harm.

Fridman argues that these sanctions were only put in place because of his Russian citizenship and his success in business. He believes that Luxembourg’s actions violated international law, particularly a treaty from 1989 between the Soviet Union an...