Why police didn't arrest the guy wearing an ISIS flag in London

Police in London have been criticized for not arresting a man who was apparently displaying an ISIS flag while walking near the Parliament, the BBC reports.

The man was carrying a small child, also waving a black flag, and his shoulders were wrapped in the black flag associated with Islamic State.

Police apparently stopped the man to talk to him but let him go because police officers decided that he was "acting within the law," the Metropolitan Police said in a statement, according to The Guardian.

Last year, Prime Minister David Cameron wrote in the Telegraph that they would stamp out poisonous extremism and that anyone walking around with an ISIS flag would be arrested.

The law states that "wearing, carrying, or displaying of an emblem or flag" is not an offense as long as there is no reasonable suspicion that the person is a supporter or member of a proscribed organization. "While support of and membership of [IS] is unlawful it is not a criminal offense to advocate the creation of an independent state," police said in a statement. 

??#ISIS flag close to #London's Big Ben,days before 7/7 anniversary ?? #UK #England pic.twitter.com/BHFWNbWP5D

- Mete Sohtaoglu (@metesohtaoglu) July 5, 2015

At least two laws in the UK could have led to this person's arrest. One from the pan-UK Terrorism Act 2000, which states that a person is committing an offense if carrying or displaying an article "in such a way or in such circumstances as to arouse reasonable suspicion that he is a member or supporter of a proscribed organisation," according to the BBC.

The other one is from the Public Order Act 1986, that states someone is guilty if they "display any writing, sign ... which is threatening or abusive within the hearing or sight of a person ..." and would cause that person harm or or distress, according to the BBC.

Police may have concluded the man didn't break any laws because no one felt harmed or distressed, a key issue of the laws, Gary Watt, a professor of law at Warwick University, told the BBC, especially since the reaction was mostly on social media and not from the people around the man.

How can someone parade around central London draped in an #ISIS flag and not be arrested under public order offence? What a joke.

- Jai Sullivan (@JaiSull) July 7, 2015

Absolutely disgusting that someone can get away with openly parading an ISIS flag, especially in the middle of London!!

- James Sidderley (@JSidderley) July 6, 2015 

Why wouldn't you arrest somebody walking through London with an ISIS flag wrapped around them oh my

- d nielle (@deeanielle) July 6, 2015

Many people were also upset that this happened so close to the ten year anniversary of the 7/7 bombings in London and the deadly attack in Tunisia in June.

Barely a week after the Tunisia attack and the day before 7/7, how can someone walk around central London in an ISIS flag not be arrested?!

- Dean Thomson (@DeaanThomson) July 6, 2015

yeah okay wearing an ISIS flag around central London in the run-up to 7/7 may not be illegal but it shouldn't be tolerated

- rhi (@rhianne_jones) July 6, 2015

Watt adds it's interesting the police didn't consider wearing the flag a "breach of the peace" under common law. 

"Had this been a naked person walking down the street would the police have intervened? They probably would have intervened even though there is no strict letter of the law against being naked in public," he told the BBC.

Police also mentioned the man's display could have been a spoof, and they still needed to confirm whether the flag was the primary one used by ISIS, accoridng to the BBC.