Arnold Schwarzenegger, the Governor of California, has brought in laws to deter celebrities and businessmen travelling to Britain to sue American-based publications in what has become known as libel tourism.
The new measures, personally signed off by Mr Schwarzenegger this week, will make judgments won against US magazines and newspapers unenforceable in California.
The legislation mirrors similar bills passed into law by the states of New York and Illinois and was strongly supported by the California Newspaper Publishers' Association.
This rash of legislation in the US follows the case of the New York-based academic, researcher and writer Rachel Ehrenfeld, who in May 2005 was ordered to pay a total of £30,000 in damages, plus costs, after being sued in the High Court in London by multimillionaire Saudi Arabian businessman Sheikh Khalid bin Mahfouz and his two sons.
They sued over Dr Ehrenfeld's book, Funding Terrorism, which was only published in the US. The High Court, which follows more libel-friendly rules than America, dealt with the case on the basis that 23 copies were sold into the English jurisdiction via the internet, and the first chapter was available on the internet.
Dr Ehrenfeld refused to respond to the litigation, and the High Court awarded summary judgment to Sheikh bin Mahfouz and his sons.
Two of the most high-profile cases of foreigners using the High Court to sue US-based publications are Cameron Diaz and Roman Polanski, who both won their libel claims.