Until the barbaric murder of David Haines, the government's main response over the summer to the prospect of terrorists returning home-raising the threat level in August from "substantial" to "severe" — seems to have been merely playing with words. Nothing much else was done, other than demanding more details of airline passengers and debating with the Lib Dems over whether returning Islamic State fighters should suffer "stronger locational constraints". For those (and I am one) who consider that the only "locational restraint" an ex-IS fighter should suffer is within a secure prison cell, this seems a woefully inadequate response to the return of "Jihadi John" and the prospect of more Lee Rigbys. However, Mr Cameron's caution is correct: most ideas from the "something must be done" brigade, calling for new laws to "control" these miscreants, are unnecessary. Their demand to stop our own citizens from returning home is legally and morally questionable: on the contrary, what we need is a full-blooded commitment to prosecute all returning IS fighters who are British citizens. This is our duty and we need no new laws to do it.

Crime against humanity: The Scottish aid worker David Haines (left) and his Islamic State murderer, who is suspected to be British

The proposals over the summer for new laws to deal with returning jihadis have included:

Reversing the burden of proof
   Both Boris Johnson and the Metropolitan Police Commissioner, Sir Bernard Hogan-Howe, want to cut "the golden thread of the criminal law" so that terrorist suspects are treated as guilty until proven innocent. Terrorism could have no greater triumph.

A terrorist Asbo
   No beheadings, presumably, after the 10pm curfew. This is a restraint for unruly youths, not for murderous fanatics.

Broader powers for the Home Secretary to deprive suspects of British citizenship
   But making your own citizens stateless is contrary to international law and to Conventions we ratified, for good reason, in 1954 and 1957. The UK has always refused to accept the right of other states to remove citizenship from their nationals resident here, and so force the UK to take responsibility for their safety and wellbeing, and we must hold ourselves to the same standard. The UK punches above its weight precisely because of its adherence, more than other powerful states, to international law and conventions. Besides which, there has for 800 years been a promise in Magna Carta (original clause 42) that all citizens have a right to return "except in the common interest of the realm for a brief period during wartime".

Bring back Control Orders
   They were abandoned for very good reason — they were ineffective, massively expensive (16 police and intelligence officers required for each order) and subject to constant judicial intervention. The only way to control an IS fighter is to confine him in prison until his case can be tried — and if he is found guilty, to confine him in prison as long as the law allows.

A new crime of going abroad to fight for terrorists
   We have an old one — the Foreign Enlistment Act of 1870, and it has never worked. It did not deter George Orwell from fighting in Spain, or ex-SAS mercenaries from training Pablo Escobar's fighters in Colombia. Will it catch Jews who move to Israel to enlist in the army and fight in Gaza?