One would have thought that Sweden's Martin Hansson and Norway's Tom Henning Ovrebro would have learned their lessons by now.
On Wednesday, in two absorbing European Champions League matches played in Portugal and Germany, the two Scandinavian referees once again were at the center of twin storms because of controversial calls that directly affected the outcome of the two round-of-16 matches.
In Portugal, Hansson, already infamous for not spotting Thierry Henry's hand ball for France in its pivotal World Cup qualifier against Ireland last fall, this time allowed FC Porto to take a quick free kick only yards from the Arsenal goal.
Radamel Falcao scored and FC Porto won, 2-1, sending Arsenal Coach Arsene Wenger off on a tirade.
In Germany, Ovrebro, famous for his confrontation with Didier Drogba after making a series of strange calls and non-calls when Barcelona defeated Chelsea in last season's Champions League semifinals, this time allowed what was clearly an offside goal by Bayern Munich to stand.
It was scored on a header by Miroslav Klose in the 89th minute and allowed Bayern to defeat Fiorentina, 2-1.
Sixteen minutes earlier, Ovrebo had reduced the Italian team to 10 men by giving a straight red card to midfielder Massimo Gobbi for barging into Bayern winger Arjen Robben on the sideline. At best, it was a yellow card infraction.
But it was Klose's headed goal -- which television replays showed was scored from a position two or more yards offside -- that was the talking point. Even Klose believed it was a bad call. "I haven't seen the replays, but I have a feeling I was offside," the veteran striker said.
"It is too often that we see officials that are not good enough to do this job," said Diego Della Valle, Fiorentina's president. "If they are not up to it, someone must tell them, and let them do something else."
The Italian team deserved to leave Munich with a tie. Robben had given Bayern the lead in stoppage time at the end of the first half with a penalty kick after a foul on Franck Ribery, but Per Kroldrup had tied it with an opportunistic goal five minutes into the second half.
Ovrebro's decisions then turned the game in Bayern's favor. "We are lucky to have won," admitted Bayern midfielder Bastian Schweinsteiger.
Meanwhile, Wenger was not about to let Hansson off the hook in Portugal.
Arsenal goalkeeper Lukasz Fabianski had gifted FC Porto a goal when he accidentally fumbled Silvestre Varela's 11th-minute cross into his own net, but Sol Campbell tied it for Arsenal with a close-range header in the 18th minute.
The controversial winning goal came six minutes into the second half. Campbell passed the ball back to Fabianski, who was obliged to play it with his feet because it was a back pass, but instead picked it up.
Hansson awarded FC Porto an indirect free kick inside the Arsenal penalty area. Before Arsenal had a chance to set up a defensive wall, Ruben Micael tapped the ball to Falcao, who steered it into the net as Arsenal's players failed to react.
"It was a legal goal, one born out of the intelligence of a Porto player," said Porto Coach Jesualdo Ferreira. Wenger thought otherwise.
"It was unbelievable that he [Hansson] allowed Porto to play the ball straightaway and push the ball into the net," Wenger said. "I have never seen that and I have been in the game a long time.
"It is completely inappropriate that he allows that in such a situation. When the referee gives the free kick, he has to allow us a chance to defend it."
Jones reported from Los Angeles.