Olympiakos were officially awarded their 39th Greek league title on Wednesday after the Hellenic Football Federation upheld a decision to punish second-placed Panathinaikos for crowd trouble at last month's Athens derby.
Violence among fans caused the derby on March 18 to be abandoned in the 82nd minute of play, with Olympiakos leading 1-0 at Athens' Olympic Stadium.
The federation's appeals committee upheld the Greek Super League disciplinary committee's decision to dock Panathinaikos three points this season and two points next season.
They also upheld the decision to award Olympiakos a 3-0 victory in the match.
Coupled with Panathinaikos' punishment, it gives Ernesto Valverde's side an unassailable 10-point lead with three matches of the Super League season remaining.
However, the federation reduced from four to three the number of home matches that Panathinaikos must play behind closed doors and also scaled back a fine from 252,500 euros ($331,000) to 212,000 euros.
A fiesta is planned for Olympiakos' last home match of the season against Corfu at Karaiskaki Stadium on Sunday.
Olympiakos have won 14 of the last 16 domestic titles and boast both the best attack in the league (62 goals) this season and the best defence (16 goals conceded in 27 matches).
Spanish coach Valverde is celebrating his third domestic title in as many seasons at the club, having led Olympiakos to the 2009 title before repeating the trick last season following an unsuccessful spell at Villarreal.