People saying the army can’t be called in, it can, it has been done before in Northern Ireland
That started with the best of intentions but didn't end well
I've posted on quite a lot of threads over the years, including this one, to explain what 'calling in the Army' means in practical terms, because there often seems to be confusion.
It's not just the Army, it is any branch of the military.
There is an established mechanism for bringing in the military - called MACA (sometimes MACP or another similar term) which is Military Assistance to Civil Authorities.
It is the department, eg the police, to say they need specific reinforcements. The MoJ then negotiates with the MoD to make the request, decide can be done and how, assign costs etc. MoD then commission the work that actually get s them there. But no one moves until recent Secretaries of State have signed off the plan.
It's limited and specific. They don't for example, take over policing (so this would not be a N Ireland scenario) but might assist police so that trained police are freed up for other tasks. So if you have, for example, a vehicle checkpoint, with one police officer and the other personnel all military, then you can have loads more checkpoints.