Why do so many people mistakenly think MPs exempted themselves from the smoking ban?

People go on and on about "one rule for us" blah blah blah. I think the press have misled the public. There is nothing in the law expressly permitting smoking in Parliament. The smoking ban DOES apply to MPs. It doesn't apply to the House of Commons, part of the Palace of Westminster, because the Crown and Crown property are not bound by ANY statutes (unless expressly stated) as a matter of tradition over several centuries (the reason why the queen only pays tax voluntarily, not compulsorily.) Since the Commons is part of a Royal Palace, the ban cannot be enforced there, though any MP caught smoking in the toilets is asking for trouble.