Why Wasn't Isaac Herzog Arrested?

It was said that Keir Starmer checked if the Israeli President, Isaac Herzog, had one of the ICJ Arrest Warrants against him for aiding and abetting War Crimes in Gaza as his statements calling for collective punishment for the October 7 attacks which was highlighted in South Africa’s case at The Hague accusing Israel of genocide before agreeing to meet him yesterday.
Somehow he hasn't which is why the Israeli head of state never left Downing Street in handcuffs and shuttled off the a prison cell in the Netherlands.
Sixty MPs from across the parties wrote to the Prime Minister to urge him to snub Herzog who was coming over to make his case against the UK government’s expected recognition of a Palestinian state.
At Prime Ministers Question Time, The Prime Minister said that he was meeting him to make 'absolutely clear that Britain condemned Israel's actions in Palesine and in the bombing of Hamas leaders in Qatar but line of the day went to the SNP's Stephen Flynn who stood up and asked if he would be inviting Vladimir Putin and Benjamin Netanyahu into No 10 next.
The New Green Party leader, Zack Polanski, called for 'handcuffs not handshakes' and said that Scotland Yard's war crimes unit should be waiting inside Number 10 to take him away for questioning.
I get that sometimes as leader you have to speak to reprehensible people and with that in mind Donald Trump is on his way here next week and there must be a case that as he is providing the weapons and financing the genocide in Gaza, he should also be feeling the hand of the War Crimes Unit on his shoulder for aiding and abetting War Crimes.