Unfortunately I don’t know the specifc answer for this – My advice is to speak to a lawyer in Portugal or speak to one of your affiliate program’s country managers as they will advuice and help you. Someone like Everest will have experts in this area.
On the whole there is always a solution so even if it proves a bit “dodgy” there are solutions afterall their are many affiliates in many jurisdictions where the law isn’t clear from Germany/Netherlands to a number of Scandinavian countries