The Man City boss has donned a yellow ribbon in recent weeks, to offer support to members of Catalonia's government who have been jailed over their part in the independence row which has been raging in recent months.
The Spaniard, who is a native of Catalonia, has worn the ribbon since his side's win over Napoli in October.
But ahead of this weekend's top-of-the-table clash, Mourinho has questioned whether his opponent should be allowed to sport such an accessory.
“I think I wouldn't be allowed to, that’s just what I think," he said.
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“If the rules allow us to do that, he is a free citizen to do it”
Jose Mourinho
“I think that our political ideology and our political beliefs is something that we have the right to have.
“We are normal citizens like everybody else in our countries and everybody else in our world.
"I've known Pep for many years, I think I know what Pep feels about his country. To have it in football, I don't know the rules.
“If the rules allow us to do that, he is a free citizen to do it.
Getty
Getty
"But I am not sure if the rules allow any political message on the pitch. That's just my doubt.
"But I know Pep and I know his feelings like everyone else because it is public about his country.”
According to FIFA, players are not allowed to publicly announce “political, religious or personal slogans, statements or images or advertising”.
However, Guardiola may escape punishment due to the fact there is no rule in place disallowing managers wearing an item of clothing or an accessory which is intended to act as a political statement.
City visit Old Trafford this weekend knowing a win will send them 11 points clear at the top of the Premier League table.