Harry might have to go into hiding. He would constantly be on the run, changing his location frequently. This would isolate him from his friends and allies. He might not be able to access the resources he needs, like his magic supplies or information from Hogwarts. And the stress of being constantly chased could also affect his mental state and his ability to use magic effectively.
He could be captured and imprisoned. If Shield is a powerful and secretive organization, they might have their own prisons or ways of detaining people. Harry would lose his freedom and might not be able to continue his normal life or his fight against the real dark forces.
It could be that there has been some sort of misunderstanding. For example, Harry might have been wrongly associated with a dark magic item or a dangerous spell. And the Shield in the fanfiction, which could be some sort of secret or powerful organization, chases him to investigate or stop him from using this supposed 'evil' power.
His relationships could be affected. Hermione and Ron might have to take on more of a caretaker role, which could change the dynamic of their friendship. Also, he may face discrimination or pity from other students at Hogwarts, which could further isolate him. And in terms of romantic relationships, his self - esteem due to his crippled state might make him less likely to pursue someone like Ginny.
Socially, his status as a hero might change. Some might see him as weakened and no longer the invincible hero. This could lead to a shift in the wizarding community's perception of him, and he might have to work hard to regain his former standing.
He might feel a great sense of betrayal. Since Gryffindor was like his home in Hogwarts, being banned could make him question his identity. He could become more isolated and withdrawn at first. However, this could also lead to him finding new friends and allies from other houses or even outside of Hogwarts.
He could be seen as an enemy. SHIELD might not take kindly to someone with Harry's potential abilities refusing to join them, and they could view him as a threat. This could lead to them trying to keep an eye on him or even take action against him if they think he's up to no good.
A consequence could be that Harry starts to feel a sense of alienation from the wizarding community. Since he is isolated by the Order, he might not be as in - touch with what's going on outside his isolation. This could lead to him making decisions based on incomplete information when he finally gets involved again. Also, his mental health might suffer as isolation can be very tough on a person's psyche, and he could become depressed or overly anxious.
One possible consequence is that he might distance himself from the Order. He could stop following their instructions or even leave the group if he feels that his anger is not being addressed or if he believes that they are not changing their ways.
Well, it might limit the spread of some fan - created works within his circle. If he is vocal about his opposition, his friends or those who respect his opinion may be less likely to engage with fanfiction.
Dudley could become more interested in the magical world. He might start to learn more about magic, spells, and the wizarding community, which could open up new perspectives for him.
It could also affect their relationship with other family members. For example, Ginny might step in to mediate between them, or it could cause tension within the family as a whole. If Albus feels unjustly yelled at, he might turn to other family members for support, which could create some family drama.