The decision was taken by the IPL Governing Council on Wednesday.
The governing council of the tournament came to the conclusion that the IPL franchises will be able to retain a maximum of five players through a combination of pre-auction retention and Right To Match (RTM) cards.
As per the report by the Indian Express, one franchise was reportedly on the side of retaining as many as five years, while another proposed retention of one player per team.
The governing council will send these options to the franchises and they will decide which of the two options to accept.
CSK and Rajasthan Royals were suspended owing to the 2013 spot-fixing scandal, which shook the league to its core and allegedly involved not just players but also some top officials of the two franchises.
The decision means CSK can call upon the likes of Dhoni, Suresh Raina and veteran New Zealand star Brendan McCullum.
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A maximum of either three retentions or three RTMs at the discretion of the franchises.
If a team does not wish to retain any player, it will still have the option of three Right to Match.
Meanwhile, the salary cap for teams for the 2018 edition is Rs. 80 crore. The IPL said the franchises will need to spend at least 75% of the salary cap each season, and that each squad should contain between 18 and 25 players with a limit of eight overseas players per franchise. The IPL has also imposed a salary cap of INR 3 crore for an uncapped player retained before the auction.
There has been a lot of brouhaha over which players would these sides retain since they had not been a part of the IPL roster past year.
The player rules for the Right to Match are maximum number of three Capped Indian players, maximum number of 2 overseas players, maximum number of 2 uncapped Indian players. The minimum base price for capped Indian players has also increased from INR 30 lakh to INR 50 lakh. Previously, uncapped Indian players had base prices of INR 10, 20 and 30 lakhs respectively; now each of those slabs has been increased by INR 10 lakh.