The government can't. Parliament can. Parliament's right is pursuant to the non obstante provisions of the Charter and is subject to renewable 5 year limits.
Section 33 of the Charter of Rights:
33. (1) Parliament or the legislature of a province may expressly declare in an Act of Parliament or of the legislature, as the case may be, that the Act or a provision thereof shall operate notwithstanding a provision included in section 2 or sections 7 to 15 of this Charter(2) An Act or a provision of an Act in respect of which a declaration made under this section is in effect shall have such operation as it would have but for the provision of this Charter referred to in the declaration.
(3) A declaration made under subsection (1) shall cease to have effect five years after it comes into force or on such earlier date as may be specified in the declaration.
(4) Parliament or the legislature of a province may re-enact a declaration made under subsection (1).
(5) Subsection (3) applies in respect of a re-enactment made under subsection (4).
Section 2 is a declaration of fundamental rights. Sections 7 to 15 enumerate a bill of rights.
um... well, as long as its simple and all