An arbitration panel convened by the Scottish FA has ruled in favour of the SPFL's decision to promote Dundee United, Raith Rovers and Cove Rangers, and confirmed the relegation of Hearts, Partick Thistle and Stranraer will stand.
Hearts and Partick Thistle took legal action against the SPFL after being consigned to the drop as a result of the vote by clubs to curtail the season amid the coronavirus pandemic.
A Court of Session hearing resulted in the case being referred to a three-person arbitration panel convened under the SFA rules with a private hearing taking place last week.
The SPFL welcomed the ruling with chief executive Neil Doncaster describing it as a "clear, comprehensive and unanimous decision".
"I am absolutely delighted that our approach has been vindicated throughout, following an intense period of legal scrutiny and review," he added.
League chairman Murdoch MacLennan added: "The panel heard from many witnesses, including senior figures from across our game and three members of the SPFL executive team. Thousands of pages of evidence were considered.
"I'm therefore very pleased that the tribunal unanimously held that the challenges to the written resolution of 15 April 2020 failed, and that the SPFL were entitled to pass, and give effect to, the written resolution and all that flowed from it."
Dundee United, who will now kick off their Premiership campaign against St Johnstone on Saturday, added: "We are pleased that today's decision by the tribunal brings this matter to a close, not just for us but for the whole of Scottish football."
A joint Statement by Heart of Midlothian FC and Partick Thistle read: "As all Parties have been requested not to comment on the tribunal's decision or reveal details of the hearings on the grounds of confidentiality, all we can only say is how disappointed and surprised we are at the outcome.
"We don't regret taking this action as it was the right thing for us to do. There were better ways to deal with ending the season, fairer ways other than putting the burden of a pandemic on to three clubs."
Scottish Premiership fixtures 2020/21: New season on Sky Sports
Celtic will kick off their Scottish Premiership title defence at home to Hamilton Academical on August 2, while Rangers travel to Aberdeen on August 1, with both games live on Sky Sports.
Neil Lennon's Celtic side, who were crowned champions for the ninth successive season in May after the SPFL opted to curtail the 2019/20 campaign, are looking for a 10th straight title, and will host the Accies at Celtic Park in a 4.30pm kick-off on the Sunday, while Steven Gerrard's Rangers are at Pittodrie at 12.30pm on the Saturday.
- Scottish Prem set for August return with new Sky Sports deal
- Sky Sports will be the only broadcaster to offer live coverage of the Scottish Premiership next season with up to 48 games available
- Find out more about Sky Sports
- All the Scottish Premiership fixtures at a glance
- Scottish Premiership - all the games live on Sky
Also on the opening week, Motherwell's trip to Ross County on August 3 will be live on Sky Sports, while all 12 Scottish Premiership teams will be shown live on Sky Sports in August, with more live fixtures to be announced from September onwards.
The first Old Firm clash of the season is scheduled for October 17 at Celtic Park, with a January 2 date for the first Ibrox clash, and another at Celtic Park on March 20 before the league split.
Champions Celtic will be live on Sky Sports four times in August - away clashes at Kilmarnock (August 9), St Mirren (August 12) and Dundee United (August 22), while Rangers will be live on Sky Sports away at Livingston (August 16) and at Hamilton (August 29).