Partygaming, like many of its peers, relies on the US for much of its customer base.
Opposition
Online gaming shares have had a rough ride in recent months thanks to two bills currently before the US House of Representatives.
One is intended to ban credit card and other electronic payments to overseas gambling sites - their main source of revenue.
A second aims to make explicit the legal underpinning for US claims that it is illegal for Americans to use overseas gaming sites.
It is this bill which came under fire in the House Judiciary Committee - unusually from a witness representing the Justice Department, which usually abhors cross-border gambling.
Currently, the situation remains unclear.
The US government argues that 1960s legislation originally designed to stamp out inter-state gambling over the telegraph system covers the internet as well.
But the World Trade Organization has said the ban has to be scrapped, after the Caribbean island of Antigua - where many offshore gambling sites base themselves - complained that the US was restricting its trade.
