Stuart Law has vowed to play for Lancashire despite his ICL connections
The rebel Indian Cricket League has threatened to take legal action if its players are banned from the Twenty20 Cup or Champions League.
England's Twenty20 Cup starts on Wednesday and the finalists go into the Champions League, yet any team fielding ICL players could then be ineligible.
ICL lawyer Jeremy Roberts told BBC Sport: "There is certainly the possibility we will take legal action.
"It would be a restraint of trade. We will discuss our next step this week."
Only three counties - Essex, Middlesex and Somerset - do not have players with ICL connections.
Yet many of the remaining 15 look set to defy guidance from the England and Wales Cricket Board and International Cricket Council by fielding ICL players in the Twenty20 Cup.
Any ICL player categorically disqualifies his team from participating in the Champions League - no exceptions will be made
Vice chairman, Indian Board
This raises the possibility that the eventual finalists could both be ineligible for September's Champions League, which will pit the sides against Twenty20 teams from India, Australia and South Africa.
The Champions League has a first prize of £2.5m, dwarfing the £100,000 awarded to the winners of the County Championship.
Cricket Australia has been charged with coming up with a definitive ruling when it formulates the Champions League rules, but their deadline for this is the ICC's annual meeting on 29 June.
This leaves the counties with a "blurred" situation, according to Surrey chief executive Paul Sheldon.
ICL lawyer Roberts, who works for the London-based firm Sheridans, warned: "Our clients (the company which owns the rights to the ICL) have always been keen to ensure that players who took part in the ICL are looked after and don't miss out on opportunities.
"At this moment, it is not clear who the legal action would be against - it could be the ECB, it could be the ICC.
"We would be very, very, very reluctant to take any action against the counties. We have tried to be really supportive of them and see them as innocent victims in all this."
Lalit Modi, the vice chairman of the Board of Control for Cricket in India and the man behind the Indian Premier League, has warned that any team with ICL players will not be allowed to compete in the Champions League.
"Any ICL player playing for any team categorically disqualifies that team from participating in the Champions League," he said.
"No exceptions will be made under any circumstances."
The counties sought clarification about this from the ECB at the weekend and were referred to guidance provided in March, which warned that an invitation to take part in the Champions League "could not be guaranteed" if they picked ICL players.
I'm going to play (in the Twenty20 Cup) and there's nothing anyone can do to stop me
Giles Clarke, the ECB chairman, insisted that the counties have been given "very clear direction".
"It is entirely a matter for them how they pick their sides," he said.
Many of the counties look set to defy the warnings when the Twenty20 Cup gets underway on Wednesday.
"We will play our strongest side," said Kent chief executive Paul Millman, whose county has two rebel players in Justin Kemp and Azhar Mahmood.
"We will get on with life, try to win the tournament and worry about India's views if and when it comes along. When the regulations become clear we will have to adjust."
Lancashire captain Stuart Law, who is contracted to return to the ICL in October to play for the Chennai Superstars, has promised to play in his side's opening Twenty20 game against Leicestershire on Wednesday.
"I'm going to play and there's nothing anyone can do to stop me," he said.