On the contrary, it's much better to have very clear text, otherwise it will turn against the citizen.

Imagine that you have an income tax where "income" isn't clearly defined. Someone will end up with an audit and a lawsuit from the tax office because their definition will be, of course, extensive (every income, including non-realized capital gains) whereas most citizens would only consider salaries.

In the end, you create legal uncertainty, and give courts way too much power.

For the record, I used to work for my country's government, and had to evaluate some laws in making that were written in an abstruse way. When I asked why, the civil servant told me that it was so "they could pick the most favorable meaning in the case of a lawsuit".