Rudolph last played for South Africa in August 2006

The South Africa batsman agreed to join the Tykes on a three-year deal.

Under ECB regulations, Kolpak players must not have played international cricket within the previous 12 months.

Rudolph last played for South Africa in August 2006, but the ECB have been forced to admit that they cannot enforce this rule under European law.

"I am just glad that the long wait is over and I can now make plans to come to Yorkshire," Rudolph, 25, said.

The Kolpak regulations allow players from countries that have associate agreements with the European Union to enjoy the same employment rights as those born within it.

It means Yorkshire can use Rudolph while also employing the Australian Jason Gillespie and Pakistani Younis Khan as the allotted overseas players.

Rudolph has had to give an sworn affadavit that he will not seek to play for the Proteas while he is under contract with Yorkshire.

An ECB statement in a letter sent to Yorkshire voiced reservations:

"The board believes applications to register players following the Kolpak ruling may not generally be in the best interests of cricket in England and Wales and hence condemns such applications."

We have reminded the ECB that we are not the first club to sign a Kolpak player and we will certainly not be the last Yorkshire chief executive Stewart Regan

Tykes chief executive Stewart Regan has defended the signing.

"We are very pleased that the ECB have accepted Jacques' registration and we now have a very strong squad for the 2007 season," he said.

"We found ourselves in a position at Christmas where we were potentially going to be without our top three batsmen from 2006 who between them scored 52% of our runs."

The three in question were ex-Australia star Darren Lehmann who has retired from county cricket, Michael Lumb who has joined Hampshire, and Anthony McGrath who recently agreed to stay at Headingley after settling a contract dispute.

Regan continued: "Our overseas batsman, Younis Khan, was potentially unavailable until after the World Cup and therefore we faced a difficult period in trying to sell memberships, renew sponsorships and generate interest in the club.