Clubs are now allowed to sign players who were out of contract before the end of the transfer window on August 31.
Under previous laws, FIFA insisted that clubs sign no players until the transfer window re-opened in the New Year.
But many leagues, including Italy's Serie A and England's Nationwide divisions, complained that the two transfer windows crippled them financially because it prevented clubs from selling players.
David Taylor, chief executive of the Scottish Football Association (SFA), said he was pleased with FIFA's decision.
"The continued efforts of the SFA, along with other associations, have persuaded FIFA to change its mind on this point. It is a sensible decision."
