He was picked up Monday at a Bogota residence on charges filed in a NY federal court alleging he conspired with three others to smuggle several tons of cocaine into the USA with a wholesale value of $15 million, or $320 million when broken up and sold on American streets.
Colombian President Juan Manuel Santos said in a televised address that his "hand wouldn't shake at the authorisation of his extradition" if irrefutable proof for the allegations exists, in order to protect the integrity of the peace deal signed in November 2016.
When Colombia's largest rebel army turned over its weapons as part of a 2016 peace deal, its leaders vowed to walk away from a lucrative cocaine business that had fueled its war on the state decades after similar leftist insurgencies elsewhere in Latin America died off.
The son of two school teachers, Santrich joined a local youth communist group as a student and entered the guerrilla movement in his early 20s. They allegedly discussed their access to coca fields, cocaine laboratories and USA -registered aircraft to smuggle the drugs.
Furthermore, FARC's National Political Council highlighted the recent national meeting of FARC reintegration territories called on former guerrilla fighters to remain calm, "to not accept provocations,"affirming "it is indisputable that they pretend to force the disbanding of the (peace) process to justify the continuation of violence".
The arrest took on added political significance because it came less than a week before President Donald Trump was set to visit Bogota for conversations with Santos partly expected to be about USA claims that Colombia's longstanding support for the drug war flagged during peace talks.
Meanwhile, ex-FARC combatants accused US and Colombian officials of orchestrating a set-up against Santrich and warned it likely will sow further skepticism among former rebels already doubtful that the government will follow through on its end of the peace accord.
Under the agreement, FARC fighters who demobilise and confess to war crimes would be spared jail time and extradition, but this protection does not extend to crimes committed after the peace deal was ratified.
Some dissident members of the FARC are said to have turned to drug trafficking and other criminal endeavors.
Colombia is now the world's largest producer of cocaine.
'Like addicts they just can't quit the business, ' he added.
However, the rebels consistently refused direct involvement in the business itself and rebel peace negotiators in 2013 denounced drug trafficking like a "scourge" that has "contaminated" the worldwide economic climate and also generated a global health catastrophe.