On 1 June this year newspaper headlines were filled with angry outpourings after a flotilla of humanitarian aid for Gaza was attacked by the Israeli navy and nine Turkish citizens were killed. This attack violated several fundamental principles of international law. The first is freedom of navigation on the high seas (UN convention on the law of the sea, article 87); the second is the protection of civilians during a state of armed conflict relating to the Gaza Strip; and the third, most fundamental, is the continuing illegal occupation of Palestinian territories (UN security council resolutions 242 and 338, passed in 1967 and 1973).

Despite universal condemnation, no legal redress has so far occurred. But then it never has.

In these circumstances, where states and governments have failed to ensure compliance with the norms of international law and justice, it is absolutely vital that the private citizen should have the right to instigate the arrest of a transgressor. This is why the justice secretary's recent announcement that the coalition intends to circumscribe the doctrine of universal jurisdiction, so that it will be far more difficult to bring anyone accused of serious human rights violations before the courts, is such a retrograde step. It sends entirely the wrong message and will be regarded by certain states as a reaffirmation of their de facto immunity. Small wonder Israel campaigned for the change and welcomed it with outstretched arms.

The proposal has its origins under Gordon Brown's Labour administration, and at the time Vince Cable and Chris Huhne, now coalition cabinet ministers, both opposed it. In 2005, an attempt was made to arrest a retired Israeli general, Doron Almog, who had arrived at Heathrow. He had been tipped off, refused to leave the aircraft and returned to Israel.

In December 2009, Tzipi Livni, Israel's former foreign minister and a member of the war cabinet responsible for Operation Cast Lead, planned to visit London. Lawyers representing innocent civilians who had suffered from indiscriminate bombardment obtained an arrest warrant for war crimes from Westminster magistrates court. In fact Livni did not arrive, probably because she had been tipped off. The warrant was withdrawn, and British politicians including Gordon Brown and David Milliband fell over themselves to apologise to the Israelis. Patricia Scotland, then attorney general, characterised the episode as "law fare". William Hague, then shadow foreign secretary, described the affair as a disgrace and said: "We cannot have a position where Israeli politicians feel they cannot visit this country. The situation is unsatisfactory and indefensible. It is absolutely my intention to act speedily." If such enthusiasm had been shown for upholding the rule of law we might be in a very different place right now.

The justice secretary's statement was based on the following reasoning:

"that universal jurisdiction cases should be proceeded within this country only on the basis of solid evidence that is likely to lead to a successful prosecution – otherwise there is a risk of damaging our ability to help in conflict resolution or to pursue a coherent foreign policy. The Government has concluded after careful consideration that it would be appropriate to require the consent of the Director of Public Prosecutions before an arrest warrant can be issued to a private prosecution in respect of an offence of universal jurisdiction".

The idea that an arrest should only take place on the basis of evidence that might lead to a successful prosecution is novel and certainly does not apply to the UK domestic jurisdiction. The Westminster magistrates court did not issue a warrant on a wing and a prayer, without proper prima facie evidence.

Our ability to help in conflict resolution, particularly in the Middle East, Iraq and Afghanistan, seems peculiarly deficient short of sending in troops. Tony Blair only emerged from the woodwork once the debacle over the flotilla forced the Israelis to reconsider the nature of their blockade. The idea of pursuing a coherent foreign policy is also not only novel but a first. Over centuries we have earned the reputation of "Perfidious Albion".

So what exactly are "the public interest" considerations that a non-political and independent director of public prosecutions has to take into account? I am less concerned about foreign politicians feeling able to visit this country than about foreign politicians feeling able to commit war crimes.

The first session of the Russell tribunal on Palestine in Barcelona in March 2010, on which I served as a member of an international jury, unanimously concluded that EU member states should ensure that universal jurisdiction laws and procedures are made as effective as possible in practice and that they make no regressive changes that would blunt the effect of existing UJ laws so as to ensure that no EU member state becomes a safe haven for suspected war criminals.

None of this is just about Israel. Is it really important in future that the Pinochets of this world are able to travel without let or hindrance and share a cup of tea with leaders like Margaret Thatcher? Good news for Henry Kissinger!

Better the words of Abraham Lincoln in 1860: "Let us have faith that right makes might; and in that faith let us to the end dare to do our duty as we understand it."

• Michael Mansfield QC is a barrister. The paperback edition of his Memoirs of a Radical Lawyer will be published in September 2010.