Lawrie, 49, told news agency AFP he faced a maximum sentence of five years after he was caught trying to bring four-year-old Afghan refugee Bahar Ahmadi to relatives in Britain from a migrant camp in Calais.
“Who in their right mind would rather a child live in a tent on a chemical dump than allow me to take that one child to her family five miles from where I live?” Lawrie said of Ahmadi, who he has nicknamed Bru.
“On that evening that I actually took her we were sat round a camp fire, Bru was sat on my knee, and she kind of just snuggled in and went to sleep, and that's the point when I just thought: 'I can't leave this girl here'.”
Lawrie, a father of four from near Leeds in central England, said Ahmadi's father had asked him several times to take his daughter across the Channel before he agreed to the risky task.
Video: Lawrie's experiences in Calais
Lawrie had visited Calais several times to build shelters for the around 6,000 migrants living in squalid conditions at a camp known as the “Jungle”, where those trying to enter Britain illegally have gathered.
On October 24th, the former soldier hid the girl in a storage compartment above the cabin of his truck, where he set up a bed.
After passing French then British customs in France and technically entering British territory, sniffer dogs detected two Eritrean migrants who, unbeknownst to Lawrie, had stowed away in the back of his truck.
Lawrie said he was then approached by a friendly French policeman.
“I walked with him. What I didn't realise at the time was that he was trying to get me back onto French soil. Because as soon as I stepped over that border, he swung round and put me into handcuffs.”
Lawrie spent three days in detention, while Ahmadi was returned to her father at the camp.
On January 14th, the Briton is due back in France for a court hearing.
“I've never run from anything in my life,” he said, vowing to face justice head-on.
“I don't have a criminal record. I know I did something illegal. But I don't think I did something morally illegal.”
Support has poured in online for Lawrie, who had put his carpet cleaning business on hold to help migrants in Calais after seeing the body of Syrian boy Aylan Kurdi washed up on a Turkish beach.
“Rob shouldn't be treated as a criminal, but as an ordinary man who was trying to do the right thing in extraordinary circumstances,” said the organizers of a petition on website 38degrees.org, which had been signed by more than 44,000 people.
A petition in French on campaigning website Change.org had gathered over 62,000 signatures by early Wednesday afternoon.
“He broke the law, but does he deserve to go to prison for showing some humanity?” the petition's organizers asked.