The Ritz Hotel's online casino has been shut down amid growing fears over the crackdown on internet gambling in the US and Europe.
"In light of the current confusion and inconsistency in online gaming legislation worldwide, the owners of The Ritz Club London Online have, regretfully, decided to close the site to new customers with immediate effect," the firm said in a statement on the site.
Sportingbet has announced its chairman has been detained in the US while travelling on non-company business.
The British online gambling firm did not say whether Peter Dicks had been arrested, but immediately asked for its shares to be suspended "pending clarification of the situation".