CHARLES Green's threat to sue the Rangers players who refused to join his newco amounted to him seeking "modern slavery", according to Wil van Megen, the head of FifPro's legal department.

Green yesterday repeated his intention to take legal action against the players who walked out on the club this week – Steven Davis, Allan McGregor, Steven Naismith, Kyle Lafferty, Steven Whittaker, Sone Aluko, Jamie Ness, John Fleck and Rhys McCabe – and he said he would also pursue transfer fees from whichever club they join.

The chief executive described their actions as opportunistic while ex-player Sandy Jardine said they had shown "greed" in leaving the club as free agents instead of even staying for a short while and leaving for transfer fees.

Most of the players who have decided to stay will report for fitness tests at Murray Park as Rangers' pre-season training programme begins under coach Kenny McDowall this morning.

Carlos Bocanegra, Maurice Edu, Alejandro Bedoya and Dorin Goian will not turn up, having been given dispensation to arrive next week because of earlier international commitments, although it is believed all four will stay at the club. Neil Alexander, Kirk Broadfoot and Kyle Hutton will also stay. Fleck became the ninth player to confirm his departure yesterday. Juanma Ortiz was in talks with the club to secure a free transfer last night rather than necessarily objecting to his contract being transferred to the newco.

Despite Green's threat of court action, the players who have decided to leave have been advised that their departures are legally sound. Dutchman van Megen from FIFpro – the federation of international footballers' unions – said Green would inevitably lose any court cases against the departing players.

Van Megen worked with FIFPro and PFA Scotland on the Andy Webster freedom-of-contract case six years ago and said that because of TUPE (Transfer of Undertakings, Protection of Employment) legislation, the Rangers players could be entirely confident of winning in any legal challenge from Green.

"He has no grounds to do that," said van Megen. "Under the European Council [EU] directive, it's quite clear that it [TUPE] has to be implemented in all countries. The Council directive is in Scottish law. The Council directive itself has a specific clause that if you refuse to go to another entity then you are free to do so, because you are not obliged to stay against freedom of labour legislation. That has to be respected. Otherwise it would be modern slavery if you were obliged to move from one entity to another.

"There is no prospect of the players being frozen out of football [pending any court cases]. They are professional footballers and the labour agreement takes precedence at stages over football regulations.

"I won't be surprised if Rangers do challenge the lawyers, because sometimes the issue pops up and clubs do challenge it. But I don't think it would be a wise decision. The players can be quite confident that they can't be forced to join the new entity."

Those who have walked out on the club were criticised by Green. "I'm very, very disappointed of course, particularly so late in the proceedings," he said. "It is clear in the regulations: if someone has an objection they have to notify within 24 hours, this is nearly two weeks [since the transfer of contracts to his newco]. I think this is just opportunism. We will definitely challenge it, yes."