The Bank of Canada wishes to inform Star Trek fans that while they may live long, they may not prosper if other parties refuse to accept defaced $5 bills.
Whoops, is that legal? In the U.S. you cannot decline payment made in cash (if you normally take cash). But it's also illegal to deface money.
But if it's not illegal to Spock a 5-spot in Canada that makes the bills legal currency still.