Domestic club rugby union within Scotland remains a predominantly amateur sport; however, semi-professional and professional outfits have been created in recent decades to participate in cross-border competitions.
With the advent of professionalism in 1995 the Scottish Rugby Union, just like the Irish Rugby Football Union, decided that existing club sides would be unable to compete with their counterparts in new cross-border tournaments such as the European Cup and Celtic League.
During the 2006-07 season an extra cup competition (The Scottish SuperCup) was introduced to replace the loss of fixtures in the Premiership due to league restricting.
For the 2009-10 season a new cross-border tournament was introduced, the British and Irish Cup which would contain semi-professional clubs from the four home nations.
Originally Scotland was represented by three sides but with restricting this has increased to four, who are determined by final positions in the League Championship.