Leading the legislative pack, the governor of Washington signed an antisypware bill today with serious penalties for violators. The law defines specific unlawful behavior, such as hijacking home and search pages, and displaying excessive numbers of pop-up ads. This law also takes on deceptive installation practices and software that reinstalls itself. The section on reinstallation makes it illegal to "Prevent, through intentionally deceptive means, an owner or operator's reasonable efforts to block the installation or execution of, or to disable, computer software by causing the software that the owner or operator has properly removed or disabled automatically to reinstall or reactivate on the computer". There's some leeway in this section, since it requires "intentionally deceptive means", which may be hard to prove in court.
Because it's a Washington state law, violations have to occur in Washington for a prosecution to take place. But since it calls for one hundred thousand dollars in damages per violation, a lot of people may consider bringing their laptop on a vacation to the state.