The way it works is, Russian oligarchs give kickbacks to Putin for the money that allows them to live luxurious lives all over the world. Making it impossible for them to do so in one of their favored locations will pressure Putin:

Looks like the UK National Crime Agency is going to start targeting Putin cronies with Unexplained Wealth Orders to confiscate their UK assets. If true, this will be a powerful step https://t.co/h4NoMXajln

— Bill Browder (@Billbrowder) June 3, 2018