WESTMINSTER is like big school.

You go there full of cocksure rebelliousness. Stupid rules - who cares about the rules. You get into fights in the playground with the older boys, and take no crap about clapping in assembly.

But "Westmonster" as some SNP people call the UK Parliament, has been around a long time. It has seen off socialists like Keir Hardie - who caused outrage because he wore a deer-stalker to parliament. It dealt with Parnell's Irish nationalists, with Suffragettes, Militant Tendency and grade-A parliamentary delinquents like our own Alex Salmond, the first MP to disrupt a Budget Speech in 1988.

And it's still there, with all its fripperies and anachronisms, like the cloak room hook to hold the Hon Member's sword. The Palace of Westminster is a powerful institution which uses its own often archaic rules and conventions as a means of diffusing political discontent.

You see it with Scotland's MPs. Suddenly they are wearing ties and suits, speaking respectfully to Mr Speaker, agreeing not to clap and promising to be "good parliamentarians". There's nothing wrong with this. SNP MPs shouldn't be uneasy about having to fit into Parliament.

Westminster is the original parliamentary democracy, after all, and it has a right to have its own rules and traditions. The secret is to use them constructively - which is what Alex Salmond always used to do - and notice the rules that really matter.

Salmond turned himself into an authority on Erskine May, the parliamentary bible. So it was hardly surprising that the former first minister last week spotted right away the devious manner in which the Conservative Government hope to introduce English Votes for English Laws (Evel).

The Government has tried to introduce Evel by using the standing orders (rules) of the Commons to set up a committee composed only of English MPs, rather than putting this important change through the two houses of parliament in proper legislation.

On the face of it, letting English MPs vote on exclusively English bills seems only fair. After all, Scotland has its own parliament in Edinburgh and can ban fox hunting without the say-so of English MPs. Surely they should have the same rights? And hasn't Nicola Sturgeon already said that SNP MPs shall not vote on English matters, like fox hunting?

That is undoubtedly true - but the problem is that they cannot have the different rights in a unitary parliament. As Alex Salmond pointed out in his intervention, Evel would "breach the fundamental principle that all members of the house are equal" .

Scottish (and ultimately Welsh and Northern Irish) MPs will suddenly find there are whole areas of legislation where they are denied a vote. This is why the Government is trying to use parliamentary sleight of hand to slip Evel through.

David Cameron hopes that once the English Grand Committee is established it will gradually be able to extend its influence. Non-English MPs will, by Commons convention, cease to vote on "English" bills.

The Scottish Government opposes this because many of these supposedly "English" bills on the NHS or income tax, have financial consequences for Scotland. It could also mean Scottish MPs becoming second-class citizens.

The House of Lords is an unelected chamber and a democratic abomination. But paradoxically it is also the place where the principles of parliamentary democracy are held in high and almost mystical regard. This is because the Lords is filled with judges and former Cabinet ministers who see themselves as guardians of the constitution against the here-today-gone-tomorrow politicians in the Commons. I suspect the UK Government knows that if it put Evel to a vote in the Lords, there would be howls of constitutional outrage and attempts to amend it.

The implications of Evel extend beyond Scotland. Imagine if Labour had won the 2010 election on the strength of its then 41 Scottish MPs? The Labour prime minister would have found himself in Parliament faced with an inability to get his legislation approved across 85% of Britain.

Say that Labour PM had tried to repeal the Health and Social Care Act, 2011, which has led to private companies invading the English NHS (but not the Scottish NHS because it is devolved). Tory MPs would uner Evel have demanded a veto on this on the grounds that they have a majority in the English Grand Committee.

It's the same with abolishing free schools, banning fox hunting, increasing income tax. It would make any government that didn't have a clear majority of English MPs practically impossible. Ed Miliband could have had a cabinet of ministers for health, education, justice etc who were in office but not in power.

Some say the SNP MPs should sit on their hands here because Evel probably just advances the day when Scotland either becomes independent, or the UK becomes federal. However, this isn't the only way in which they risk being outmanoeuvred in the chess game that is parliamentary process.

Under the Scotland Bill to implement the Smith reforms, Holyrood is, apparently, to get powers to increase welfare benefits, if it wishes, and income tax powers to pay for them. This is such a transparent trap I can't quite believe the SNP has fallen into it - but they signed up to Smith last year.

The Scottish Parliament is not getting powers to vary any of the other big taxes like National Insurance, VAT and Excise Duties. Also, benefits such as Disability Living Allowance (DLA) are already in line to be cut by 20% under the Tory Government's welfare crackdown.

Labour will say: put your money where your mouths are and increase income tax on the rich. But with only around 19,000 Scots or so earning over £150K, just increasing the top rate of tax to 50% isn't going to be enough even to restore benefits to existing levels.

At most the 50p tax could earn around £100 million and wouldn't be enough even to make up the cut in DLA - let alone anything else. The Scottish Government will be under pressure to increase the basic rates as well.

The Tories think the SNP will come an electoral cropper trying to raise tax on ordinary Scots to pay for all those Benefits Street "wastrels" - as many tabloids seem to regard welfare recipients. The Tories are convinced the Scots are just as phobic about income tax as English voters.

They hope that promising to cut income tax at the next Holyrood election is the key to letting the Conservatives replace Labour in Scotland as the main opposition party. This is why the Scotland Bill is being rushed through practically before the SNP MPs have got their bums on the green benches.

The SNP do not have any presence in the House of Lords, which is where most of the action on constitutional bills like Smith takes place. So, this bill could be on the statute books within months and certainly in time for the Holyrood elections in May.

The Scotland Bill places a fiscal time bomb under Holyrood. The SNP MPs need to get to grips with it fast. The risk is that their MPs will get diverted, wasting time fighting meaningless parliamentary conventions while they're being stitched up behind their backs.