Hansson awarded a free-kick to Porto after Sol campbell had passed back to goalkeeper Lukasz Fabianski, who picked up the ball.
Porto star Ruben Micael took the set-piece quickly and passed it to Falcao, who sent the ball past Fabianski before Arsenal had managed to regroup.
“I thought that what the referee has given as a back-pass was completely accidental because it was a toe-kick which you never do as a defender,” Wenger told Sky Sports.
“I think the referee also has to give us time to build a wall or else you will never have a chance to defend an indirect free-kick in the box.
“It is laughable. It is not defendable from the referee and it is difficult to understand.
“Has he ever played football? If he has played I don’t see how he can explain to me how we can defend.”