The independent professional body, which governs solicitors in England and Wales, said lawyers are duty bound to represent their clients whoever they might be to ensure the legal process remains fair.
The comments come after Foreign Secretary Liz Truss said the government had received "threatening letters" from law firms representing Russian individuals and companies seeking to avoid sanctions in the wake of the country's invasion of Ukraine.
Truss has said the government has a "hit list" targeting oligarchs and their families and was working at the law firms, press agencies and accountants supporting them. Opposition Labour Party MP Ben Bradshaw urged the government to name the law firms stalling sanctions.
But Law Society president I. Stephanie Boyce said it was the solicitors' job to ensure the government is abiding by its own rules.
"This is how the public can be confident they live in a country that respects the rule of law — unlike Putin's tyrannical regime," Boyce said.
If solicitors challenge the government's sanctions, "it's because they think the government is at risk of breaking its own rules," Boyce added.
The growing pressure has led some firms to review and even cut their ties with Russian clients. Both Linklaters and Baker McKenzie have said they would examine their links, while Norton Rose Fulbright has forbidden its lawyers from commenting publicly on sanctions.
The U.K. government accelerated measures targeting dirty money laundered through London's financial system by Russian oligarchs on Monday after accusations that it had delayed introducing new legislation. The Economic Crime (Transparency and Enforcement) Bill, introduced on Monday, is meant to unmask anonymous foreign owners of U.K. property and give the authorities greater powers to seize criminal wealth.
Western governments have toughened up economic sanctions against Moscow in response to its invasion of Ukraine. They have cut off selected Russian banks from the SWIFT global financial messaging system and blocked the country's central bank from liquidating assets held abroad.
--Additional reporting by Richard Crump. Editing by Joe Millis.
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