In my briefing last month, I explained that US patent litigation is governed by the American Rule pursuant to which the prevailing party is not automatically allowed to recover its attorney fees. Rule 54(d) of the Federal Rules of Civil Procedure, however, states that "costs other than attorneys fees shall be allowed as of course to the prevailing party unless the court otherwise directs". The US Supreme Court has explained that Rule 54 does not provide "unrestrained discretion to tax costs to reimburse a winning litigant for every expense he has seen fit to incur in the conduct of his case" (Farmer v Arbian Am Oil Co, 379 US 227, 235 (1964)). Rather, federal courts are bound by 28 USC Section 1920, which expressly lists the kinds of expenses that a federal court may tax as costs, and the courts have stated that Section 1920 thereby imposes "rigid controls" on cost-shifting in federal courts ((Crawford Fitting Co v J T Gibbons, Inc, 482 US 437, 444 (1987)).