Biggar have launched an appeal against the decision to declare the 2019-20 Scottish rugby season null and void.
With an unassailable lead at the top of the National One league, Biggar have already received the trophy.
But their path to the Premiership was blocked by Scottish Rugby's ruling on Tuesday.
The club say being denied a second successive promotion due to the coronavirus shutdown will have "massive ramifications".
The SRU decision follows similar moves by the Irish, Welsh and Italian unions.
However, Newcastle Falcons are being promoted to England's Premiership to replace Saracens, who had their relegation confirmed earlier this year following salary cap breaches.
In a brief statement, Biggar add that their situation is made "all the more galling" by the RFU in England promoting and relegating "based on the fact that 80% of their season was complete".
Biggar had won 18 of their 20 league matches and were 19 points clear of Heriot's, who had three matches remaining.