A street trader will learn on Tuesday whether he has won his battle to continue selling unofficial Arsenal merchandise.
The Premiership champions are asking European judges to stop Matthew Reed selling goods using the club name, its shield and its cannon emblem.
If the decision goes against the club there could be far-reaching implications for the entire football memorabilia market, which is worth millions of pounds a year.
The High Court originally threw out the case because Arsenal produced no evidence to show that customers were led to believe the souvenirs were club approved.
Show support
Lawyers for the club, which makes £5m a year from souvenirs, argue that it has exclusive rights to the names 'Arsenal' and 'Arsenal Gunners' and the team's shield-and-cannon designs.
It registered its name and logos in 1989, by which time Mr Reed had been in business outside the club's Highbury stadium for nearly 20 years.
Mr Reed says he simply uses the name and logos to give fans the chance to show their support.
He says a sign on his stall makes it clear the hats and scarves are unofficial.
'Commercial use'
Earlier this year European Court of Justice's Advocate-General suggested that the club did have a case.
Damaso Ruiz-Jarabo said Mr Reed was not entitled to use Arsenal's trademarked logos for commercial purposes.
"Use of a trademark by anyone other than the proprietor with the purpose of supplying goods in the market... constitutes commercial use."
His opinion was not a verdict, however, and does not bind the court when it makes its decision.