Earlier quoted context omitted.
Lobbying in some form is explicitly protected by the 1st amendment. The question is: If you form a contract for someone else to petition for a redress of greivances on you behalf, is that contract void?
1st amendment rights apply to people. They should not apply to corporations.
How would you go about restricting corporate speech without restricting people's speech?
And, more so, why would you want to?
Scenario A: 1,000 people organize into a company. One of those people is the Founder/CEO who takes the vast majority of the money out of the company into his personal wealth. It is uncontested that this natural person can then use his wealth to buy ads/throw big dinner parties and invite politicians/etc. right?
Scenario B: 1,000 people organize into a company. They distribute the money of the company relatively equally, meaning that no single person in the company has enough money to buy ads/throw big dinner parties and invite politicians/etc. But they think it's important for their company to lobby. But in your world, they can't.
What principle is being served here? Make sure that only the personally wealthy can speak? That doesn't sound amazing.
What exact types of groups do you want to deny speech rights to? "Company" is a vague term. Do you want to deny speech rights to non-profits? To political parties? If you deny speech rights only to corporations organized under certain for-profit tax rules, do you imagine that it would be hard for Amazon to work around that rule?