The Financial Services Roundtable, which represents many large US banks, insurance and securities firms, released this estimate. The AML (anti-money laundering) spending has increased 50 percent since 2002.
The Financial Times article (May 11, 2005) that cited the estimate did not break out legal costs from other compliance costs, but given the close relationship between compliance and law (See my posts of March 26, 2005 on second class citizens and May 20, 2005 on merging compliance and law under the GC.) I assume a fair portion of the spending goes to inside lawyers and outside counsel.