Andrew Hall, Justin Kemp and Johannes van der Wath are free to play county cricket as Kolpak players after winning an appeal against their bans on Wednesday.
The England and Wales Cricket Board refused to accept the South African trio's registrations due to their participation in the 'rebel' Indian Cricket League last winter.
But a three-man appeal tribunal ruled in favour of the players, who can now take up their original contracts, Hall and van der Wath with Northamptonshire and Kemp at Kent.
None of the trio count as overseas players under the EU Court of Justice's Kolpak ruling.
"We are delighted that both Andrew and Johannes are now available for us for 2008," Northamptonshire said in a statement of their official website.
"This strengthens our playing squad and enables us to push for honours in all competitions.
"We are looking forward to having both players with us as soon as possible."
A fourth ICL 'rebel' - Jamaican Wavell Hinds - was also banned by the ECB but did not appeal and has subsequently signed to play for Derbyshire as an overseas player during the Twenty20 Cup.