Formula One drivers have been told they cannot wear earrings and chunky jewellery during races for safety reasons.
An International Automobile Federation (FIA) spokesman said the 'ban on bling' was approved by the governing body's medical commission after a meeting of the FIA's world motor sport council in Paris on Wednesday.
The final paragraph of an FIA statement detailing decisions taken noted that there would be an immediate ban "on the wearing of jewellery (body piercing and heavy chains) by race and rally competitors."
Klien will be racing on Sunday while Liuzzi drives the third car in Friday practice only.
Ferrari's seven-times world champion Michael Schumacher, hoping to rebound from a poor start to the season with a new car this weekend, wears a lucky amulet given to him by his wife Corinna.
The FIA did not say how the measures would be policed or what sanctions might apply.
Other measures adopted by the FIA at the meeting included agreement that Formula One's technical regulations will remain unchanged until the end of the 2007 season.
There will also be no limits on the number of tyre suppliers until at least 2008.
All teams will be invited to discuss the 2008 technical regulations at a meeting on April 15 with further meetings if necessary.
The new regulations for 2008 must be published by the end of this year under the existing 'Concorde Agreement' that governs the sport.
At present only champions Ferrari have agreed to extend the Concorde Agreement beyond its expiry at the end of 2007.
The other nine teams have reserved judgement and shunned a meeting attended only by the FIA and Ferrari in January to discuss regulation changes.Five of Formula One's major carmakers are planning their own series from the end of 2007, offering teams that sign up with them a far greater share of the revenues as well as a 'level playing field'.