In fact, they will say this because they had come to know the reality which they were concealing before. As a matter of fact even if they be sent back, they would certainly repeat the same things which they had been forbidden to do. Indeed they are liars.
Meaning:-
Concealing: to hide, to keep secret, to prevent or avoid disclosing, keep secret.
Forbidden: refuse to allow (something), prohibit, not allowed, banned.