Do the Conservatives know what the House of Commons is actually for?

This is ridiculous:

A Tory government will introduce a law guaranteeing no rise in income tax rates, VAT or national insurance before 2020, David Cameron is to announce.

The Conservative leader will pledge legislation within 100 days of assuming office to ensure rates do not rise in the next Parliament.

The law is not a plaything, what exactly is the point of this idea? Just make a promise and keep to it, how hard can that be? Oh yes, 'no top down reorganisation of the NHS', immigration, I see your point. I could just about see the point of the fixed term parliaments act, and we've bee spared 18 months of wittering about when the election is going to be. But simply passing a law which says that you will do what you've said you'll do is both a betrayal of the purposes of law, and a very revealing act in itself. It's an admission that, whatever politicians say, we can't trust them. 

Two questions

1. Will David Cameron be arrested and tried if the Conservatives do raise income tax, VAT or NI? And I'm assuming that not raising thresholds at least in line with inflation counts as a tax rise. 

2. How do we know they will keep this promise? The promise itself is only made because we know that politicians don't keep their promises, but it's subject to the same trust deficit. As far as I know, the LibDems are the only party in recent political history to have made a promise, broken it, and then admitted that they broke it and apologised. 

Could we pass a law making political gimmicks illegal? David Cameron seems to think that just about anything can be turned into a short-term electoral asset: the unity of the UK, the legislative system, fear. Stop for a minute and think, please.

In the meantime, if you want to pass a popular law, how about one forcing Conservatives to turn up to election debates ?