The Football Association has deducted three points from Arsenal Ladies for fielding an unregistered player, England international Katie Chapman.
The punishment follows Chapman's substitute appearance against Liverpool on 3 August, a game Arsenal won 3-0.
The match was Chapman's first following the birth of her third child.
Arsenal, third in the Women's Super League with one match, remaining, now cannot qualify for next year's Champions League through the league.
The Gunners have won the women's title - the Women's Premier League and latterly Women's Super League - a record 14 times.
They have also appeared in the Champions League, or its previous incarnation the Uefa Women's Cup, every season since 2004-05. They can still qualify if they win the tournament this season.
Chapman, 31, won the last of her 82 England caps in 2010 when her central contract was cancelled.
She recently claimed the FA dropped her from the England squad in 2010 following her request to take time off to look after her family.