You're familiar with section 129 of the Criminal Code, which states that anyone who “omits, without reasonable excuse, to assist a public officer or peace officer in the execution of his duty in arresting a person or in preserving the peace, after having reasonable notice that he is required to do so” is guilty of “an indictable offence and is liable to imprisonment for a term not exceeding two years”.
That is the provision of the Criminal Code on obstruction. You're familiar with it, right?