How sure can you be that your lobby is successful? Can you like 'buy' a politician, effectively a legal bribe, or is it more nuanced? In the EU, a lot of laws

How sure can you be that your lobby is successful? Can you like 'buy' a politician, effectively a legal bribe, or is it more nuanced? In the EU, a lot of laws are effectively written or co-authored by companies, which saves the politicians and their staffs incredible amounts of time and expertise. This must be quite expensive, just to have the lawyers on payroll who are able to do that.